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If correctly selected, it reaches terminal velocity, which can be measured by the time it takes to pass two marks on the tube. Electronic sensing can be used for opaque fluids. Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes' law can be used to calculate the viscosity of the fluid. A ...
The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface. The sum of friction drag and pressure (form) drag is called viscous drag.
Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. [7] [8] Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. [9] [10] [11] Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body.
is the flow velocity relative to the object, is the reference area, and; is the drag coefficient – a dimensionless coefficient related to the object's geometry and taking into account both skin friction and form drag.
Consequently, the acceleration is the second derivative of position, [7] often written . Position, when thought of as a displacement from an origin point, is a vector: a quantity with both magnitude and direction. [9]: 1 Velocity and acceleration are vector quantities as well. The mathematical tools of vector algebra provide the means to ...
Shear velocity, also called friction velocity, is a form by which a shear stress may be re-written in units of velocity.It is useful as a method in fluid mechanics to compare true velocities, such as the velocity of a flow in a stream, to a velocity that relates shear between layers of flow.
If the speed of the vehicle decreases, this is an acceleration in the opposite direction of the velocity vector (mathematically a negative, if the movement is unidimensional and the velocity is positive), sometimes called deceleration [4] [5] or retardation, and passengers experience the reaction to deceleration as an inertial force pushing ...
For so-called "Stokes' drag" the force is approximately proportional to the velocity, but opposite in direction: =, where: b {\displaystyle b} is a constant that depends on the properties of the fluid and the dimensions of the object (usually the cross-sectional area ), and