Steady state simulation of flow over a throttle body

OBEJECTIVES: Simulation of flow over a throttle body using converge studio cfd software. Simulation is carried for two different mesh conditions and analysed with respective to the velocity profile at the outlet of the flow. Once the mesh is refined well ,the simulation is carried out for differnt CFL no and checked for stability and analyzed with respect to mass flow rate. Since the flow is steady , the thrittle valve is stationary.

Geomerty:

Boundry conditions:

Inlet: Inflow PBC with 0.15 MPa

Outlet:Outflow PBC with 0.1 MPa

Throttle valve: Stationary wall

Elbow body: Wall

Air is used as fluid with O2 and N2 mass fraction of 0.23 and 0.77 respectivly. Temp maintained at 300 K

Meshing:

Meshing technique used by Converge studio is called \"Cut cell cartesian method\" or \"Adaptive grid refinment\" method.

Fixed embedding:

Emedidding refers to local mesh refinement. In this embedding is done to the throttle valve with embedded layer as 2 and permanet mode anf sacling of 2 for coarse and 3 for fine mesh.

The total cells for coarse and fine mesh are represented below

sl no Mesh Total cell

1 Coarse 16014

2 Fine 41454

Coarse mesh

Fine Mesh

Base grid of 2mm

Results:

Although the velocity is converged for the both the cases, there is some slight difference during the flow. Since the domain is simple this velocity change is small. This change in values due to mesh effects majorly in the complex structures.

Above fig shows the oulet velocity profile for different meshes. Althought the velocity is converged in both the cases, there is slight difference during the flow. Since the domain is simple this velocity change is small. This change in values due to mesh effects majorly in the complex structures.

Above fig represnts the velocity flow over the domain

Above fig represnts the pressure variation on the thrittle valve due to velocity. We can observe the flow hits the valve, high pressure is created showing red in color and less pressure in opposite side of flow. This reprents that the flow is correct.

Mass flow rate:

The CFL condition is measured using velocity, space and time-step giving the equn

CFL=u*dt/dx

Above fig shows Out let mass flow rate

Above fig shows inlet let mass flow rate

Here we can observe that the mass flow rate satisfies the continuity eqn in all the cfl cases. The variation in the mass flow rate can be easily observed in all the cases. This is becasuse of different cfl number, in this we can say that for higher cfl number converges faster. Althoughthese varoation are smaller an idel cfl value depends on the flow domain and flow characteristics.

Animation of steady state flow over throttle body:-