contains 206 terms · This page displays 30 terms, you can enter keywords to query the complete range
Chemical Engineering热惰性热惰性（thermal inertia），也称为热惯量，常用于描述在传热过程中观测到的物体温度响应延迟。该现象产生于物体相对于其环境既能存储热量又能传输热量的能力。由于系统组分的构型与传热方式（例如传导、对流、辐射、相变）以及能量存储形式（例如内能、焓、潜热）在不同实例间差异显著，因此不存在对热惰性具有普适适用性的封闭形式数学表达式。 具有较大质量和热容量的实体通常表现出较慢的温度响应。然而，仅以热容量来量化热惰性并不充分。对热惰性的测量还取决于热流在体内与体外的分布情况，需根据系统的边值问题予以判断。 热惰性是内含及外延性质取决于语境。一些作者将其作为一种材料的强度性属性来识别，例如与热逸散率相关联时。也有人根据系统在瞬态传热过程中的时空行为对其作为外延量进行评价。在这种基于测量或数值模拟的空间—时间行为分析中，有时可用一个时间常数作为所选组件或子系统热惰性的简单参数化表示。
Thermal inertia is a term commonly used to describe the observed delays in a body's temperature response during heat transfers. The phenomenon exists because of a body's ability to both store and transport heat relative to its environment. Since the configuration of system components and modes of transport (e.g. conduction, convection, radiation, phase change) and energy storage (e.g. internal energy, enthalpy, latent heat) vary substantially between instances, there is no generally applicable mathematical expression of closed form for thermal inertia. Bodies with relatively large mass and heat capacity typically exhibit slower temperature responses. However heat capacity alone cannot accurately quantify thermal inertia. Measurements of it further depend on how heat flows are distributed inside and outside a body, in accordance with system boundary conditions. Whether thermal inertia is an intensive or extensive quantity depends upon context. Some authors have identified it as an intensive material property, for example in association with thermal effusivity.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 导热垫是电脑或电子学中用到的装置，是固体材料（石蜡或硅氧树脂）事先成形的方形或长方形薄片，一般会放在散热片下方，让要散热的设备（像中央处理器或集成电路）可以进行热传导，将热带到铝或铜材质的散热片。导热垫及导热化合物是用来填补在热传导过程中，固体和固体表面形成的热接面空隙。若固体表面光滑平坦，应该就不需要导热垫了。导热垫一般在室温下是硬的，但在高温下会变软，因此可以填补固体之间的空隙。 导热垫可以代替散热膏作为热界面材料。有些AMD及Intel的中央处理器在散热片下方也有导热垫，好处是比较干净，比较容易安装。不过导热垫的导热效果不如散热膏。
In computing and electronics, thermal pads (also called thermally conductive pad or thermal interface pad) are pre-formed rectangles of solid material (often paraffin wax or silicone based) commonly found on the underside of heatsinks to aid the conduction of heat away from the component being cooled (such as a CPU or another chip) and into the heatsink (usually made from aluminium or copper). Thermal pads and thermal compound are used to fill air gaps caused by imperfectly flat or smooth surfaces which should be in thermal contact; they would not be needed between perfectly flat and smooth surfaces. It is an alternative to thermal paste to be used as thermal interface material. AMD and Intel have included thermal pads on the bottom of heatsinks shipped with some of their processors, as they are cleaner and generally easier to install. Some, but not all, types of chip carriers include thermal pads in their design. Thermal pads are relatively firm at room temperature, but become soft and are able to fill gaps at higher temperatures such as those generated by a working chip.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 湍流普朗特数（英语：turbulent Prandtl number，记作Prt）， 是流体力学中的一个无量纲量，表示动量涡流扩散系数与传热涡流扩散系数的比值，可用于湍流边界层的传热问题。根据雷诺比拟得到的湍流普朗特数的理论值为1。不过雷诺比拟有时会失效，通过实验得到的湍流普朗特数则为0.7到0.9不等，取决于流动的分子普朗特数及其他参数。
The turbulent Prandtl number (Prt) is a non-dimensional term defined as the ratio between the momentum eddy diffusivity and the heat transfer eddy diffusivity. It is useful for solving the heat transfer problem of turbulent boundary layer flows. The simplest model for Prt is the Reynolds analogy, which yields a turbulent Prandtl number of 1. From experimental data, Prt has an average value of 0.85, but ranges from 0.7 to 0.9 depending on the Prandtl number of the fluid in question.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 在辐射热传中，视界因子（view factor） F A → B {\displaystyle F_{A\rightarrow B}} 定义为从表面 A {\displaystyle A} 离开的辐射中，碰到表面 B {\displaystyle B} 的比例 。在比较复杂的情境中，离开任一表面 A {\displaystyle A} 的辐射可能到达许多不同的平面，可以分为许多平面或平面区段计算后再相加。有时也称为配置因数（configuration factors），形状因数（form factors），角度因数（angle factors）或形状因数（shape factors）。
In radiative heat transfer, a view factor, F A → B {\displaystyle F_{A\rightarrow B}} , is the proportion of the radiation which leaves surface A {\displaystyle A} that strikes surface B {\displaystyle B} . In a complex 'scene' there can be any number of different objects, which can be divided in turn into even more surfaces and surface segments. View factors are also sometimes known as configuration factors, form factors, angle factors or shape factors.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 滴是几乎或完全由自由表面包覆的极小量液体。当液体在铅直的管子末端或其他表面边界处积聚时，可能会形成悬挂的液滴，称作悬滴。液滴也可由蒸汽遇上冰冷的表面冷凝成露或较大量的液体雾化形成。 数学上，垂直管状物体末端水滴的最大可承受重量可以此计算： m g = 3 π a λ cos α {\displaystyle mg=3\pi a\lambda \cos \alpha } mg ，又即 W ，为液滴的重量； π 为圆周率； a 为管口半径； λ 为液体的表面张力； α 为接触角度（液面与刚体接触点的延伸切线与刚体平面之间的角度）。这个关系是简单地量度表面张力的基础，常用于石油工业。 此外，由于水和空气的折射率，光线折射和反射在雨珠表面，导致彩虹的形成。
A drop or droplet is a small column of liquid, bounded completely or almost completely by free surfaces. A drop may form when liquid accumulates at the end of a tube or other surface boundary, producing a hanging drop called a pendant drop. Drops may also be formed by the condensation of a vapor or by atomization of a larger mass of solid. Water vapor will condense into droplets depending on the temperature. The temperature at which droplets form is called the dew point.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 底波拉数（Deborah number，De）是流变学中的一个无量纲量，用来描述材料在特定条件下的流动性。若时间够长，本质类似固体的物质也有可能会流动，若快速形变，本质类似流体的物质也有可能会有类似固体抵抗形变的特性。底波拉数就是将上述的观察量化，驰豫时间较短的物质比较容易流动，其应变衰减也会比较快。 底波拉数是假设在时间足够的条件下，即使是最坚硬的物体（例如山）也会流动。因此流动特性不是一个材料本身的固有属性，而是一种相对属性，此相对属性和二个有本质上完全不同的特征时间有关。
The Deborah number (De) is a dimensionless number, often used in rheology to characterize the fluidity of materials under specific flow conditions. It quantifies the observation that given enough time even a solid-like material might flow, or a fluid-like material can act solid when it is deformed rapidly enough. Materials that have low relaxation times flow easily and as such show relatively rapid stress decay. The Deborah number was originally proposed by Markus Reiner, a professor at Technion in Israel, who chose the name inspired by a verse in the Bible, stating "The mountains flowed before the Lord" in a song by the prophetess Deborah in the Book of Judges; הָרִ֥ים נָזְל֖וּ מִפְּנֵ֣י יְהוָ֑ה hā-rîm nāzəlū mippənê Yahweh).
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 胀流性（Dilatant），又称为剪切增稠（英语：shear thickening），是指剪切速率或者剪应力增加到某一个数值时，液体中形成了新的结构，引起了阻力的增加，导致液体的表观粘度增大，同时伴随着体积的胀大的现象。 胀流性流体是非牛顿流体中的一种，与之相反的是剪切稀化流体。 具有胀流性的流体称为胀流性流体（dilatant fluid），大多数固体含量多的流体都是属于这一类的。这类流体在静止时，流体中的固体粒子处在堆砌得很紧密的状态，粒子间空隙很小并充满液体。当作用在悬浮液上的剪应力很大或者剪切速率很快的时候，粒子的移动速度较快，粒子间的空隙增大，悬浮体系的总体积增大，粒子间移动时的润滑作用减小，阻力增大，引起了流体表观粘度增大，从而致使在流动过程中能耗增大，增加剪切力并不能成比例的增大剪切速率。这种性质正好与剪切稀化流体的流动性质相反。 常见的胀流性流体有陶瓷泥浆，糖果配料，玉米淀粉以及沙水混合物等含高度抗絮凝固体的流体。
A dilatant (, ) (also termed shear thickening) material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the initialism STF, is an example of a non-Newtonian fluid. This behaviour is usually not observed in pure materials, but can occur in suspensions. A dilatant is a non-Newtonian fluid where the shear viscosity increases with applied shear stress. This behavior is only one type of deviation from Newton's law of viscosity, and it is controlled by such factors as particle size, shape, and distribution. The properties of these suspensions depend on Hamaker theory and Van der Waals forces and can be stabilized electrostatically or sterically. Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation. A large portion of the properties of these systems are due to the surface chemistry of particles in dispersion, known as colloids.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 阻力危机（也称为Eiffel悖论）是一种流体力学的现象，是流场的雷诺数增加到一定程度时，其阻力系数突然下降的现象。针对圆形物体（例如球或是圆柱）的阻力危机现象已有详尽的研究 。当雷诺数增加到大约300000时，阻力系数会快速的由0.5变成0.2，此时会产生较窄的紊流尾流。阻力危机的现象也和物体的表面粗糙度有关。
In fluid dynamics, the drag crisis (also known as the Eiffel paradox) is a phenomenon in which drag coefficient drops off suddenly as Reynolds number increases. This has been well studied for round bodies like spheres and cylinders. The drag coefficient of a sphere will change rapidly from about 0.5 to 0.2 at a Reynolds number in the range of 300000. This corresponds to the point where the flow pattern changes, leaving a narrower turbulent wake. The behavior is highly dependent on small differences in the condition of the surface of the sphere.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 迪恩数（D，De或Dn）是流体力学中的无因次量，会用在弯管及弯曲渠道的流体研究中，得名自1920年代研究弯曲流场的英国科学家威廉·雷金纳德·迪恩。
The Dean number (De) is a dimensionless group in fluid mechanics, which occurs in the study of flow in curved pipes and channels. It is named after the British scientist W. R. Dean, who was the first to provide a theoretical solution of the fluid motion through curved pipes for laminar flow by using a perturbation procedure from a Poiseuille flow in a straight pipe to a flow in a pipe with very small curvature.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 焰（英语：flame）又称火焰、火苗、明火，是物质燃烧产生的火中的发光部分。与之相对的，不发光的部分称为烟。没有明火，仅冒烟的燃烧称为闷烧。
A flame (from Latin flamma) is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction made in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density, they are then considered plasma.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 电渗流或电渗效应是于多孔介质、微通道、及其它流体管道两端施加电压时造成的流体流动。电渗流速度与管道尺寸无关，但是流体于压力梯度的关系尺寸大的管道中会更明显。电渗流对小尺寸流动意义更为重大。电渗流是化学分离技术中的重要技术，特别是毛细管电泳。电渗流可以发生在自然的未过滤的水中，如缓冲溶液。
In chemistry, electro-osmotic flow (EOF, hyphen optional; synonymous with electro-osmosis or electro-endosmosis) is the motion of liquid induced by an applied potential across a porous material, capillary tube, membrane, microchannel, or any other fluid conduit. Because electro-osmotic velocities are independent of conduit size, as long as the electrical double layer is much smaller than the characteristic length scale of the channel, electro-osmotic flow will have little effect. Electro-osmotic flow is most significant when in small channels, and is an essential component in chemical separation techniques, notably capillary electrophoresis. Electro-osmotic flow can occur in natural unfiltered water, as well as buffered solutions.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 埃克曼数（Ekman number，简称Ek）是用来描述海洋及大气的地球物理学现象的无量纲数。埃克曼数是流体的黏滞力和行星自转产生的科里奥利力的比值，埃克曼数得名自瑞典海洋学家沃恩·华费特·埃克曼。 埃克曼数也可以应用在任何旋转的流场中，此时，埃克曼数是其黏滞力及科氏力的比值。当埃克曼数小时，扰动在受摩擦力影响而消失之前就会开始传播。埃克曼数描述埃克曼层厚度的量值，也就是粘滞力和科里奥利力平衡的特殊边界层。
The Ekman number (Ek) is a dimensionless number used in fluid dynamics to describe the ratio of viscous forces to Coriolis forces. It is frequently used in describing geophysical phenomena in the oceans and atmosphere in order to characterise the ratio of viscous forces to the Coriolis forces arising from planetary rotation. It is named after the Swedish oceanographer Vagn Walfrid Ekman. When the Ekman number is small, disturbances are able to propagate before decaying owing to low frictional effects. The Ekman number also describes the order of magnitude for the thickness of an Ekman layer, a boundary layer in which viscous diffusion is balanced by Coriolis effects, rather than the usual convective inertia.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 埃克曼输送是指风引起的海水流动。风吹拂表层海水时海面会被施加摩擦力，从而牵引上层10-100米厚的水体随之运动。但由于受科里奥利力的影响，即海水在运动时会受到与运动方向呈90°夹角的力作用，导致水体运动方向与风向产生偏角。输运方向取决于所在半球：北半球水体运动方向沿风向顺时针偏转，南半球则逆时针偏转。这一现象最早由弗里乔夫·南森记录，他在1890年代的北极探险中发现冰层移动方向与风向存在夹角。
Ekman transport is part of Ekman motion theory, first investigated in 1902 by Vagn Walfrid Ekman. Winds are the main source of energy for ocean circulation, and Ekman transport is a component of wind-driven ocean current. Ekman transport occurs when ocean surface waters are influenced by the friction force acting on them via the wind. As the wind blows it casts a friction force on the ocean surface that drags the upper 10–100m of the water column with it. However, due to the influence of the Coriolis effect, as the ocean water moves it is subject to a force at a 90° angle from the direction of motion causing the water to move at an angle to the wind direction. The direction of transport is dependent on the hemisphere: in the Northern Hemisphere, transport veers clockwise from wind direction, while in the Southern Hemisphere it veers anticlockwise. This phenomenon was first noted by Fridtjof Nansen, who recorded that ice transport appeared to occur at an angle to the wind direction during his Arctic expedition of the 1890s.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 动压（英语：dynamic pressure）是一个与流体力学有关的物理量，其定义为： q ≡ 1 2 ρ v 2 {\displaystyle q\equiv {\frac {1}{2}}\rho {{v}^{2}}} 其中的符号代表（使用国际单位制）：
In fluid dynamics, dynamic pressure (denoted by q or Q and sometimes called velocity pressure) is the quantity defined by: q = 1 2 ρ u 2 {\displaystyle q={\frac {1}{2}}\rho \,u^{2}} where (in SI units): q is the dynamic pressure in pascals (i.e., N/m2), ρ (Greek letter rho) is the fluid mass density (e.g. in kg/m3), and u is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume. For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and static pressure.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 喷气发动机（英语：Jet engine）是一种通过加速和排出的高速流体做功的热机或电机。它既可以输出推力，也可以输出轴功率。 大部分喷气发动机都是依靠牛顿第三定律工作的内燃机，但也有一些例外。常见的喷气发动机有涡轮风扇发动机、涡轮喷气发动机、超音速燃烧冲压发动机、冲压发动机、脉冲压式喷气发动机等。
A jet engine is a type of reaction engine, discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition may include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as a turbojet, turbofan, ramjet, pulse jet, or scramjet. In general, jet engines are internal combustion engines. Air-breathing jet engines typically feature a rotating air compressor powered by a turbine, with the leftover power providing thrust through the propelling nozzle—this process is known as the Brayton thermodynamic cycle. Jet aircraft use such engines for long-distance travel. Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines. They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 开尔文-亥姆霍兹不稳定性（英语：Kelvin–Helmholtz instability，名称来自开尔文男爵和赫尔曼·冯·亥姆霍兹）是在有剪力速度的连续流体内部或有速度差的两个不同流体的界面之间发生的不稳定现象。 一个例子是风吹过水面时，在水面上表面的波的不稳定。而这种不稳定状况更常见于云、海洋、土星的云带、木星的大红斑、太阳的日冕中。
The Kelvin–Helmholtz instability (after Lord Kelvin and Hermann von Helmholtz) is a fluid instability that occurs when there is velocity shear in a single continuous fluid or a velocity difference across the interface between two fluids. Kelvin-Helmholtz instabilities are visible in the atmospheres of planets and moons, such as in cloud formations on Earth or the Red Spot on Jupiter, the atmosphere of the Sun, and the surface of the Sun.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 无黏性流（英语：inviscid flow）是指没有黏度的理想流体产生的流场。 无黏性流的黏度趋近于零，因此雷诺数会趋近无限大。若忽略黏滞力时（就像无黏性流的情形），描述流体力学的纳维-斯托克斯方程会简化成欧拉方程。简化后欧拉方程可以适用于无黏性流，前提是流体的黏度低，雷诺数远大于1。利用欧拉方程可以求解许多低黏度时的流体力学问题。但是，若在固体边界附近的流场（边界层），或是有明显速度梯度的流场（速度梯度是因为黏滞力造成的），黏度可以忽略的假设就不适用了。 超流体的流场就是无黏性流。 无黏性流又可以再分类为无旋性的位流，以及有旋性的无黏性流。
In fluid dynamics, inviscid flow is the flow of fluid that is not viscous. The principles of inviscid flow can also be applied to the flow of fluids of low viscosity in regions of the flow field where it is known there is little viscous activity. The Reynolds number of inviscid flow approaches infinity as the viscosity approaches zero. Where viscous forces are non-existent the Navier–Stokes equations can be simplified to a form known as the Euler equations. This simplified equation is derived by considering an inviscid fluid. Using the Euler equation, many fluid dynamics problems involving low viscosity are easily solved; however, the assumption of negligible viscosity is not valid in the region of the flow field near a solid boundary (the boundary layer) or, more generally in regions with large velocity gradients which are evidently accompanied by viscous forces. The flow of a superfluid is inviscid.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 在流体动力学上，开尔文环流定理（英语：Kelvin's circulation theorem，由第一代开尔文男爵威廉·汤姆孙于1869年发表，因此以他命名）描述在彻体力保守的正压理想流体中闭合曲线（包围相同的流体元）的环量在流体运动时并不会随时间而改变。其数学描述为 D Γ D t = 0 {\displaystyle {\frac {\mathrm {D} \Gamma }{\mathrm {D} t}}=0} 其中 Γ {\displaystyle \Gamma } 为材料围线 C ( t ) {\displaystyle C(t)} 的环流。用更简单的话来说，这条定理所指的是，若观察闭合围线并注意它一段时间（注意所有流体元的运动）的话，则始终两者间的环流相等。 本定理在有黏性应力、非保守彻体力（例如科里奥利力）或非正压的压力－密度关系的情况下并不成立。
In fluid mechanics, Kelvin's circulation theorem states:In a barotropic, ideal fluid with conservative body forces, the circulation around a closed curve (which encloses the same fluid elements) moving with the fluid remains constant with time. The theorem is named after William Thomson, 1st Baron Kelvin who published it in 1869. Stated mathematically: D Γ D t = 0 {\displaystyle {\frac {\mathrm {D} \Gamma }{\mathrm {D} t}}=0} where Γ {\displaystyle \Gamma } is the circulation around a material moving contour C ( t ) {\displaystyle C(t)} as a function of time t {\displaystyle t} .
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 射流（jet，fluid jet）又称喷流，是喷射到周围介质中的束状流体，通常来自某种喷嘴、孔或孔口。 射流可以前进很长距离而不耗散。 与周围的流体介质相比，射流流体具有更高的动量。如果射流周围的介质与射流由相同的流体组成，并且该流体具有粘度，则周围流体会在称为卷吸的过程中被射流携带前进。
A jet is a stream of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating. Jet fluid has higher speed compared to the surrounding fluid medium. In the case that the surrounding medium is assumed to be made up of the same fluid as the jet, and this fluid has viscosity, some of the surrounding fluid is carried along with the jet in a process called entrainment. Some animals, notably cephalopods, move by jet propulsion, as do rocket engines and jet engines.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 在流体力学中，Kc数（Keulegan–Carpenter number）是一个无量纲数，用来描述一个在振荡流场中的物体，所受到的阻力相对惯性力之间的关系，也可可以用在一物体在静止流体中振荡的情形。Kc数小表示惯性力的影响比阻力要大，Kc数大表示（紊流）阻力的影响较大。 Kc数的定义如下 K C = V T L , {\displaystyle K_{C}={\frac {V\,T}{L}},} 其中 V为流速振荡的振幅（若是物体振荡的情形，则为物体速度的振幅） T为振荡的周期 L为物体的特征长度，若物体为一圆柱，其特征长度为其直径。 在探讨海浪对沉积物运移的影响时，会使用另一个相关的位移参数δ（displacement parameter）来表示： δ = A L , {\displaystyle \delta ={\frac {A}{L}},} 其中 A为在振荡流场中流体粒子的偏移幅度，若流场以弦波运动，A可以用V和T表示A = VT/(2π)，则 K C = 2 π δ .
In fluid dynamics, the Keulegan–Carpenter number, also called the period number, is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow. Or similarly, for objects that oscillate in a fluid at rest. For small Keulegan–Carpenter number inertia dominates, while for large numbers the (turbulence) drag forces are important. The Keulegan–Carpenter number KC is defined as: K C = V T L , {\displaystyle K_{C}={\frac {V\,T}{L}},} where: V is the amplitude of the flow velocity oscillation (or the amplitude of the object's velocity, in case of an oscillating object), T is the period of the oscillation, and L is a characteristic length scale of the object, for instance the diameter for a cylinder under wave loading. The Keulegan–Carpenter number is named after Garbis H.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 朱林定律（英语：Jurin's Law）描述液体在毛细管中上升或下降的规律。此定律的文字表述是：在确定的温度下，液体在毛细管内升高的最大高度和毛细管的直径成反比。其数学表达式为： h = 2 γ cos θ ρ g r 0 {\displaystyle \qquad h={\frac {2\gamma \cos \theta }{\rho gr_{0}}}} 其中 h {\textstyle h} 是毛细管内液体的最大高度； γ {\textstyle \gamma } 是液体的表面张力； θ {\textstyle \theta } 是液体和毛细管壁间的接触角； ρ {\textstyle \rho } 是液体的密度； g {\textstyle g} 是重力加速度； r 0 {\textstyle r_{0}} 是毛细管的半径。
Jurin's law, or capillary rise, is the simplest analysis of capillary action—the induced motion of liquids in small channels—and states that the maximum height of a liquid in a capillary tube is inversely proportional to the tube's diameter. Capillary action is one of the most common fluid mechanical effects explored in the field of microfluidics. Jurin's law is named after James Jurin, who discovered it between 1718 and 1719. The difference in height between the surroundings of the tube and the inside, as well as the shape of the meniscus, mathematical expression of this law can be derived directly from hydrostatic principles and the Young–Laplace equation. Jurin's law allows the measurement of the surface tension of a liquid and can be used to derive the capillary length.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 佩克莱特数是流体力学中的无量纲数，指流体中对流和扩散质量、热量之比，计算式为： P e = R e P r = V L α {\displaystyle \mathrm {Pe} =\mathrm {Re} \mathrm {Pr} ={\frac {VL}{\alpha }}} 其中： R e {\displaystyle \mathrm {Re} } 为雷诺数 P r {\displaystyle \mathrm {Pr} } 为普朗特数 V {\displaystyle V} 为平均流速 L {\displaystyle L} 为特征长度 α {\displaystyle \alpha } 为扩散系数或热扩散率 佩克莱特数以Pe表示，是一个无因次参数，用来表示对流速率与扩散速率之比。若Pe >> 1，表示流速大，扩散十分缓慢，故当物质被带往下游时，扩散云团之尺度几乎不变，扩散云团可视为一凝结云团向下游平移，扩散对浓度的影响可予以忽略。反之，当Pe << 1时，表示扩散十分快速，而扩散主导浓度的变化。
In continuum mechanics, the Péclet number (Pe, after Jean Claude Eugène Péclet) is a class of dimensionless numbers relevant in the study of transport phenomena in a continuous environment. It is defined to be the ratio of the rate of advection of a physical quantity by the flow to the rate of diffusion of the same quantity driven by an appropriate gradient. In the context of species or mass transfer, the Péclet number is the product of the Reynolds number and the Schmidt number (Re × Sc). In the context of the thermal fluids, the thermal Péclet number is equivalent to the product of the Reynolds number and the Prandtl number (Re × Pr).
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 沥青滴漏实验（英语：Pitch drop experiment）是一个长期实验，其目的是为了测量极高黏度沥青在室温环境下的流动速度。这个实验由澳大利亚布里斯班昆士兰大学在1927年开始进行。当时的托马斯·帕内尔教授把一些沥青放进一个封了口的漏斗内，至1930年，漏斗封口被剪开，沥青开始缓慢流动。每一滴高黏度沥青需经近十年时间，方能滴进漏斗下方的烧杯之中，第一滴沥青于1938年12月滴出。时至今日，已滴出九滴沥青。 从实验的结果当中，人们可计算到沥青的黏度大约是水之千亿倍。 一直到1988年以前，由于该实验周围的环境并没有特别控制，因此其沥青流动速度会因温度的变化而改变，但第7滴之后装了冷气使温度固定。 帕内尔教授于1948年9月1日逝世后，实验改由约翰·梅因斯通（John Mainstone）教授负责，他与帕内尔教授于2005年凭着这个实验，而获得搞笑诺贝尔奖。梅因斯通教授于2013年8月23日逝世后，实验续由安德鲁·怀特（Andrew White）教授负责。 根据吉尼斯世界纪录，这个实验是全球持续时间最长的实验，而漏斗内的沥青也足够使这个实验再进行几百年。
A pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. "Pitch" is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen, also known as asphalt. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ P波（英语：primary wave）是在地震发生时最先被地震仪记录下来的地震体波。穿越地球内部的波（例如，地震波）被称为体波。相对于体波的是面波。体波可以分为P波和S波。P波意指（primary wave）或是压力波（pressure wave）。在所有地震波中，P波传递速度最快。因此发生地震时，P波最早抵达测站，并被地震仪纪录下来，这也是P波名称的由来。P波的P也能代表压力（pressure），来自于其震动传递类似声波，属于纵波的一种（或疏密波），传递时介质的震动方向与震波能量的传播方向平行。 对于地球内部构造的了解和推论，大部分是借由观测地震波中的体波。地震波在不同介质有不同传播时间和路径，在介质交界面时会引起反射、折射，以及相位的改变。地震学家利用这些特性来获得地球内部资讯。当体波穿越地球液态层时，P波在经过下部地幔与外地核时会稍许折射。造成P波在104°至140°间会有阴影区，令地震仪无法记录。
In continuum mechanics, a P wave (primary wave or pressure wave) is one of the two main types of elastic body waves or seismic waves. P waves travel faster than other seismic waves and hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P waves may be transmitted through gases, liquids, or solids.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 水处理时，会透过常不同药剂进行絮凝以利除去水中悬浮物质，例如为混拟使用之硫酸铝、氯化铁、PAC等混拟剂等，以及强化胶凝作用之各种助凝剂等，为调整酸碱度之石灰、苏打等碱剂，或硫酸等酸剂、消毒用之氯剂，吸附用之活性炭等等，该等药剂，或为液体，或为固体均应依一定之剂量连续或间歇性注入处理水体进行净化工作，为此净水厂内就需要不同用途之加药设备。 药品处理设备处应不同水质处理之需要，根据实验比较效果与经济所得最合适之药品及剂量配置外，应同时考虑选用其他药品及剂量之可能性，为药剂应在卫生上对水质无不良影响者为限。
In colloidal chemistry, flocculation is a process by which colloidal particles come out of suspension to sediment in the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended, under the form of a stable dispersion (where the internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation) and are not truly dissolved in solution. Coagulation and flocculation are important processes in fermentation and water treatment with coagulation aimed to destabilize and aggregate particles through chemical interactions between the coagulant and colloids, and flocculation to sediment the destabilized particles by causing their aggregation into floc.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 重结晶（英语：Recrystallization），再结晶，晶种结晶法，也称之为优先结晶法；是一种物理过程，在化学、冶金学和地质学中有很不同的用途。
Recrystallization is a broad class of chemical purification techniques characterized by the dissolution of an impure sample in a solvent or solvent mixture, followed by some change in conditions that encourages the formation of pure isolate as solid crystals. Recrystallization as a purification technique is driven by spontaneous processes of self-assembly that leverage the highly ordered (i.e. low-entropy) and periodic characteristics of a crystal's molecular structure to produce purification.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 扬谷，又称扬场，系农业上将谷物与谷壳分离的方法，亦能除去储藏谷物中的象鼻虫或其他害虫。扬谷前须先脱粒（将农作物籽粒与茎秆分离）。 手动扬谷方式系将谷物与谷壳的混合物抛至空中，风会吹走较轻的谷壳，而较重的谷物则会落下。扇车则是代替人手进行扬谷的农业机械。
Winnowing is a process by which chaff is separated from grain. It can also be used to remove pests from stored grain. Winnowing usually follows threshing in grain preparation. In its simplest form, it involves throwing the mixture into the air so that the wind blows away the lighter chaff, while the heavier grains fall back down for recovery. Techniques included using a winnowing fan (a shaped basket shaken to raise the chaff) or using a tool (a winnowing fork or shovel) on a pile of harvested grain.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 蒸馏器是一种用于蒸馏液体（混合物）的大型装置，其原理是加热后利用混合物内不同物质沸点不同，使得不同的液态物质在不同的温度下沸腾，然后再度使蒸气冷凝。 蒸馏器已被用于生产香水、药品、注射用水、蒸馏酒以及分离和提纯各种化学品。
A still is an apparatus used to distill liquid mixtures by heating to selectively boil and then cooling to condense the vapor. A still uses the same concepts as a basic distillation apparatus, but on a much larger scale. Stills have been used to produce perfume and medicine, water for injection (WFI) for pharmaceutical use, generally to separate and purify different chemicals, and to produce distilled beverages containing ethanol.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 升华是指一种物质从固态不经过液态直接转化为气态的过程，是物质的一种物态变化。与升华相反的过程称做凝华，指物质从气态直接变成固态。这样的例子有结霜。升华是吸热的反应，所需的焓是汽化热和熔化热之和。
Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the intermediate liquid state. The verb form of sublimation is sublime, or less preferably, sublimate. Sublimate also refers to the product obtained by sublimation. The point at which sublimation occurs rapidly (for definition, see below) is called critical sublimation point, or simply, sublimation point. Notable examples include sublimation of dry ice at room temperature and atmospheric pressure, and that of solid iodine with heating. The reverse process of sublimation is deposition (also called desublimation), in which a substance passes directly from a gas to a solid phase, without passing through the intermediate liquid state. Technically, all solids may sublime, though most sublime at extremely low rates that are hardly detectable under usual conditions. At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gas state requires an intermediate liquid state.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗ 盐析（英语：salting out）是在溶液中加入无机盐类而使某种物质溶解度降低而析出的过程或方法。 蛋白质的分子颗粒直径在0.1—0.001μm，属于胶体范围。在蛋白质溶液中加入无机盐（如硫酸铵、硫酸钠、氯化钠等），会吸引大量水分子与这些无机盐离子水合，于是蛋白质表面暴露出来的疏水性区域增加，彼此靠着疏水性作用力结合，而从溶液中沉淀，这种作用便称为盐析。 值得注意的是，盐析相对于盐溶（salting in），是一个可逆过程，可将盐析出来的蛋白质再次溶于水而不影响原蛋白质的性质。不同的无机盐对盐析的作用是不同的，同一种盐对于不同蛋白质的作用效果也是不同的。所以，在某些实验，可利用盐析分离出不同的蛋白质。
Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength. Salting out is typically used to precipitate large biomolecules, such as proteins or DNA. Because the salt concentration needed for a given protein to precipitate out of the solution differs from protein to protein, a specific salt concentration can be used to precipitate a target protein. This process is also used to concentrate dilute solutions of proteins. Dialysis can be used to remove the salt if needed.
Sources, licensing and use
Wikipedia contributors · Retrieved2026-10-04 · CC BY-SA 4.0. Introductions were extracted as plain text and shortened. Language versions may emphasize different aspects.For concept reference; consult the original standards for authoritative requirements.
View content license ↗