 ## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

• Masooma_Qizilbash12
Subscriber

hello all,

I want to ask how I know the values to be enter in the initialization tab of ansys fluent package 2020 R2 for turbulanet kinetic energy and specific dissipation rate if i have a beaker and in beaker there is 1%PVA and 0.2 % PEI are mixing at the impeller speed of 5000 rpm total volume of the sytem is 1010 ml 1000ml pva and 10 ml pei.

thank you

regards,

masooma

• omkar.kulkarni
Ansys Employee

Hello,

You will need some more parameters to calculate the TKE and specific dissipation rate. You can refer the following formulas and calculate it accordingly.

1. TKE=1/2 (ρuu′)

• TKE is the turbulent kinetic energy.
• ρ is the density of the fluid.
• u' represents the fluctuating velocity (the deviation of the local velocity from the mean velocity).

2. ε=2μ/ρ[(xj/ui)(xj​/ui)]

• ε is the specific dissipation rate.
• μ is the dynamic viscosity of the fluid.
• ρ is the density of the fluid.
• (xj/ui) represents the velocity gradient in the fluid, with and denoting the different spatial coordinates.

I hope this helps.

Thanks.

• Masooma_Qizilbash12
Subscriber

thank you Omkar for the reply,

I want to know that I have only one velocity of 5m/s how can I calculate the velocity deviation from local velocity to mean what this gradient means also for TDR what is this velocity gradient because in a stirred tank impeller is moving with 5000 rpm only one velocity

I shall be thankful fo the help

kind regards,

masooma 