## What are particle laden fluids?

Particle-laden flows refers to **a class of two-phase fluid flow** in which one of the phases is continuously connected (referred to as the continuous or carrier phase) and the other phase is made up of small immiscible and typically dilute particles (referred to as the dispersed or particle phase).

## How are Stokes numbers calculated?

The Stokes number is the ratio of relaxation time to hydrodynamic time: **St=2/9 (a/L)^2 Re/R** where a is the particle radius L is the hydrodynamic length scale (size of the computational domain) and Re=U0*L/nu is Reynolds of the flow.

## What is Saffman lift force?

**lateral lift force on particles**. This lift force is technically called “Saffman force”.

## What is dispersed flow?

**characterized by the flow where one phase is dispersed in the other continuous phase**. This flow configuration is observed in all types (gas-liquid gas-solid liquid-liquid and liquid-solid) of two-phase flows as shown in Figure 1.

## What is a Stokes particle?

**a measure of flow tracer fidelity in**particle image velocimetry (PIV) experiments where very small particles are entrained in turbulent flows and optically observed to determine the speed and direction of fluid movement (also known as the velocity field of the fluid) …

## What is particle Reynolds number?

**a dimensionless number**(i.e. it has no units) that is a measure of the type of flow through a fluid. In the case of falling particles this describes the way that air flows around the particle.

## What is Strouhal number?

**the ratio of inertial forces due to the local acceleration of the flow to the inertial forces due to the convective acceleration**. … At high Strouhal numbers oscillations dominate the flow while at low Strouhal numbers the oscillations are swept by the fast-moving fluid.

## What is virtual mass force?

The virtual mass also known as added mass or apparent mass is **associated with the force required to accelerate the fluid surrounding a moving body of different phase**. It has the effect of liquid retarding interpreted as inertia force acting on the accelerating bubble.

## What causes slug flow?

**a wave is picked up periodically by the rapidly moving gas to**form a frothy slug which passes along the pipe at a greater velocity than the average liquid velocity.

## What is a single phase fluid?

Single-phase Fluid Flow

Classic study of fluid dynamics concentrates on the flow of a single homogeneous phase e.g. **water** air steam. All of the fluid flow equations and relationships discussed normally in this section are for the flow of a single phase of fluid whether liquid or vapor.

## What is bubbly flow?

**fluid moves as small dispersed bubbles through a continuous fluid**. … Bubble flow normally occurs at low flow rate and low holdup of the bubbly fluid. As the velocity of the continuous fluid increases the bubbles are dispersed into smaller more widely separated bubbles.

## Which shape particles are assumed in Stokes law?

**Spherical particles**. Homogeneous (uniform in composition) material.

## What are the four conditions of Stokes law?

Conditions under which Stoke’s law is valid are:

**The fluid through which the body moves must have infinite extension**. The body is perfectly rigid and smooth. There is no slip between the body and the fluid. The motion of the body does not give rise to turbulent motion.

## What is Stokes law write its condition?

Stokes’ law is a law in physics that states that **the force that resists a sphere’s fall in a viscous fluid is directly proportional to the velocity of the sphere the radius of the sphere and the viscosity of the fluid**. … r is the radius of the sphere.

## How high can Reynolds number be?

**between 3 000 and 5 000**.

## How is flow described using the Reynolds number?

**the ratio of the inertial forces to the viscous forces**. This ratio helps to categorize laminar flows from the turbulent ones.

## What will be the critical Reynolds number in pipe flow?

For flow in a pipe of diameter D experimental observations show that for “fully developed” flow the critical Reynolds number is about **Re _{d}_{ }_{crit} = 2300**. Laminar flow. For practical purposes if the Reynolds number is less than 2000 the flow is laminar.

## What is vortex shedding effect?

**when the wind blows across a structural member**vortices are shed alternately from one side to the other and where alternating low-pressure zones are generated on the downwind side of the structure giving rise to a fluctuating force acting at right angles to the wind direction (Fig.

## How do you pronounce Strouhal?

## How do I stop vortex shedding?

The entrainment of fluid into the inner side of the separated shear layers is obstructed by the downstream splitter plate. Our results suggest that by **attaching in-line splitter plates both upstream and downstream of the cylinder** the vortex shedding can be suppressed as well as a reduction in drag be obtained.

## What is Basset history force?

**for the viscous effects**and describes the force due to the lagging boundary layer development with changing relative velocity (acceleration) of bodies moving through a fluid. It is known as the ‘history’ term in the force equation.

## What is induced mass?

Applications. The added mass can be incorporated into most physics equations by considering an effective mass as the **sum of the mass** and added mass. … For a general body the added mass becomes a tensor (referred to as the induced mass tensor) with components depending on the direction of motion of the body.

## Can added mass be negative?

Negative added mass also occurs **when one or more elements of the structure enclose a portion of the free surface** for example a pair of surface-piercing cylinders in two dimensions [3 4 5].

## What is Slug water?

• A slug discharge is **any discharge including an accidental spill which has the potential to cause interference or pass through of a POTW**.

## What is slug or plug flow?

**smaller than the tube**. Slugs are similar in dimension to the tube diameter. The slugs travel at a speed that is a substantial fraction of the gas velocity and occur intermittently.

## How do you stop slugs from flowing in pipes?

**Using a low point effluent drain or bypass**. Reducing line sizes to the minimum permitted by available pressure drops. Arranging the pipe configuration to protect against slug flow.

## What is two-phase flow pipe?

Two-phase flow is **a flow in which two different aggregate states of a substance or of two different substances are simultaneously present**. The possible combinations include gaseous/liquid (see Gas content of fluid handled) gaseous/solid and liquid/solid (see Solids transport).

## What is single-phase and multiphase?

A multiphase system which is distinguished from a single-phase system by the presence of one or more interfaces separating the phases can be considered a field that is divided into single-phase regions by those interfaces—or moving boundaries—between phases.

## How is cavitation formed?

Cavitation occurs when **a pressure drop occurs within a region of a fluid to a point below the vapor pressure of the fluid at the current temperature**. At this point the state change from liquid to gas occurs creating a bubble.

## What is Stokes law and factor involved in Stokes law?

In Stokes’s law the drag force F acting upward in resistance to the fall is **equal to 6πrηv** in which r is the radius of the sphere η is the viscosity of the liquid and v is the velocity of fall. …

## What are the Stokes assumption?

In order to apply this to the Navier–Stokes equations three assumptions were made by Stokes: **The stress tensor is a linear function of the strain rate tensor or equivalently the velocity gradient**. The fluid is isotropic. For a fluid at rest ∇ ⋅ τ must be zero (so that hydrostatic pressure results).

## What is Stokes law in physics class 11?

**The force that retards a sphere moving through a viscous fluid is directly ∝to the velocity and the radius of the sphere**and the viscosity of the fluid.

## What is the upper limit of particle size for which Stokes law applies?

The lower limit of particle size for the validity of Stoke’s Law is 0.0002 mm. However the upper limit for the same is **0.2 mm**.

## What are the limitations of Stokes law?

**equation may not show the real sedimentation rate**. High solid content imparts additional viscosity to the system which must be taken into consideration if the correct rate of settling is to be determined. The equation contains only the viscosity of the medium.

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## Viscosity of particle laden films