Learning Forum

[Thodorisdm]

Dear, 

I am using the Euler-Lagrange approach to simulate the trajectories of solid particles( d=3-4mm) in my flow (Re up to 10^4). 

I am planning to use the spherical drag law. However, when checking up to which Reynolds number the a1, a2, a3 coefficients are calculated, I found that the maximum Re is 5*10^4. Therefore, my questions is what happens to the regions in my flow which have a higher Re than that? How is the Cd calculated there? Is it constant? 

Thank you in advance. 

Kind regards, 

[SRP]

 

Hi,

The drag will be calculated based on changing the ampltitude of the particle Reynolds number and fitting to the experimental results based on changing three coefficients.

Hope you find this useful.

Thank you

Saurabh

 

[Amine Ben Hadj Ali]

The default spherical drag law will take care about having higher Reynolds-Number range (so more or less Newtonian drag for solid particles). Check the Theory Guide to know more about Morsi-Alexander drag law.

[Thodorisdm]

Thank you for the answers. 

1. Could you specify the chapter that explains more about Morsi-Alexxander drag law? Because in chapter 12.3.1 it does not specify anything about the abovementioned drag law, it only gives the formula.
2. I dont understand what do you mean by will take care since the are no coefficients (no function) for Reynolds numbers above 50000, as you can see in the picture attached. Or may I understood something wrong?

Thank you in advance

[Amine Ben Hadj Ali]

Multiphase Chapter under Fluid-Fluid Exchange Coefficient (Using Search feature is helpful). Fluent formulation does not cap at 50000. Validation and deployment of any correlations are something else which can be discussed.

 

[Amine Ben Hadj Ali]

If you are concerned with drag in supercritical region then you probably need to implement your own corrleation.

[Thodorisdm]

I found the chapter you were referred to and it is has clarified how is the Morsi and Alexander drag law formulated in Fluent. 

For people who might have the same question in the future : Fluent uses the coefficients from the above image with only difference found in the regions defined. Moreover, the last particle Reynolds number is defined as Re_p>= 10000 which is a valid assumption up to Re_p <= 2*10^5