Froude number - Wikipedia
The Froude number enters into formulations of the hydraulic jump (rise in with the Reynolds number, it serves to delineate the boundary between laminar and. Free surface: interface between two fluids of different density Navier-Stokes Equations. 2. 2. 2. 2. 2. 2. 2 Characterized by Reynolds number: Re characterized by the Froude number. U Hydraulic depth (D): ratio of flow area to top width. equations include average flow velocity. understanding of how the Reynolds and Froude numbers change along a stream where the Explain the relationship between channel geometric characteristics and stream flow characteristics at a.
For example, for a pipe, L is the diameter of the pipe.
A small Reynolds number implies that the viscous effects are important, while the inertial effects are dominant when the Reynolds number is large. The models are designed for dynamic similarity on Reynolds law, which states that the Reynolds number for the model must be equal to the Reynolds number for the prototype.
According to Reynolds model law, models are based on Reynolds number.
Models based on Reynolds number includes: Pipe flow Resistance experienced by sub-marines, airplanes, fully immersed bodies etc. The scale rations for time, acceleration, force and discharge for Reynolds model law are obtained as Problem 1: A pipe of diameter 1.
The Continuity Equation, the Reynolds Number, the Froude Number
Tests were conducted on a 15cm diameter pipe using water at Find the velocity and rate of flow in the model. For rectangular cross sections, the hydraulic depth is the water depth. Hydraulic depth Physically, the Froude number represents the ratio of inertial forces to gravitational forces.
This form is similar to the Mach Number in air.
Froude model law is the law in which the models are based on Froude number which means for dynamic similarity between the model and prototype, the Froude numbers for both of them should be equal. Froude model law is applicable when the gravity force is only predominant force which controls the flow in addition to the force of inertia.Reynolds Number
Froude model law is applied in the following fluid flow problems: Free surface flows such as flow over spillways, weirs, sluices, channels etc…… Flow of jet from an orifice or nozzle, Where waves are likely to be formed on surface. Where fluids of different densities flow over one another. A force of 2N is required to tow the model. If we want to perform an experiment, say measuring the drag force on an aircraft, we often build a scale model of the aircraft and place it in an appropriate flow.
Clearly in this case the model should be an exact scale model. If it is, then we say the two flows the real aircraft and the model posess geometric similarity.
Dynamic similarity occurs if the forces acting on equivalent bodies in the two flows are always in the same ratios. For the real and model aircraft example, this means that the ratio is the same as the ratio In this particular case, dynamic similarity occurs when the Reynolds numbers are the same for the aircraft and for the model.
Under these circumstances the dimensionless lift and drag coefficients CL, CD will be the same, and so we can use experimental results from the model to predict the forces acting on the whole aircraft. For any type of flow we can construct appropriate dimensionless groups, and if the values of the groups are the same for two flows then the two flows are dynamically similar.
The groups are always constructed from characteristic scales in the problem, for instance a characteristic length L or a characteristic speed V. Some important dimensionless groups include Reynolds: The Reynolds number is a measure of the ratio of the inertia of the fluid to the viscous forces.
Its value is indicative of whether the fluid is laminar or turbulent. The Froude number is a measure of the ratio of inertia to gravitational forces, and is important for free surface flows.