We can see the separation of the boundary layer towards the back of the cylinder, this area has slightly less pressure than the same point in the front of the cylinder. Here we can see at very low Reynolds number that the flow does not separate and the pressure gradient pushes the flow around the body.
The three examples below show steady state flow at different velocities of air. For low Reynolds numbers this will be around the cylinder, but for larger to see the vortices the computational domain extends past the model. To do this I modelled a cylinder of diameter 50mm with an extrusion of 200mm, the extrusion length is arbitrary as I used a 2D computational domain.Įditing the definition of the domain to better show the areas of interest. In this section I will take a look at recreating some results from these studies to show the difference in Reynolds number to the flow. There are numerous peer reviewed studies on the effects of flow around bluff bodies. In the next example we will discuss external flow over a bluff body. We can see the validation for a very simple section of pipe. We can then set a surface goal to get the velocity at the outlet.Īs we can see here SOLIDWORKS is able to accurately solve for the outlet velocity. In SOLIDWORKS We set the inlet boundary condition to 2m/s and the outlet to environmental pressure. Working this out by hand we use the equation:Īssuming the Density does not change we can remove and rearrange for V2 If the inlet velocity of the water is 2 m/s what is the velocity at the outlet? The reduction in area should lead to an increase in Velocity of the fluid. The nozzle above goes from having a 0.5m Diameter to a 0.25m diameter. With a few boundary conditions defined by the user SOLIDWORKS solves the equations for us. These are complex equations to solve for humans, luckily computers are excellent at solving equations. These equations solve for the continuity of mass and momentum and state that the mass times the acceleration is proportional to the force acting on a fluid particle.
Navier Stokes equation for incompressible flow in the x,y,z directions respectively. SOLIDWORKS flow simulation solves studies using the Navier Stokes equations which are outlined below. SOLIDWORKS Flow Simulation Vs Hand Calculations