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Probleme on the turbulence
Posted 2010/02/26 4:19 GMT-5 Version 3.5a 2 Replies
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I'm modeling the impact of a droplet onto a substrate using the level set method . i use the module: two phase flow, laminar, level set.
when I increase the impcat velocity, I added the turbulence model and when I click to solve my problem, I got the message bellow:
Time-dependent solver/Generalized alpha
Number of degrees of freedom solved for: 271446
Step Time Stepsize Res Jac Sol Order Tfail NLfail
0 0 out 3 2 2 0
Error:
Failed to find consistent initial values.
Sqrt_of_negative
Function: sqrt
Failed_to_evaluate_expression
Expression: nojac(((min((ck_chns*sqrt((((taum_chns*res_v_chns)^2)+((((res_p_chns*tauc_chns)/(nojac(sqrt((u2int_g1_chns/vol_g1_chns)))*nojac((rhoint_g1_chns/vol_g1_chns)))))^2+((taum_chns*res_u_chns))^2)))),U_ref_chns)*0.5)*min((gijgij_chns^-0.25),((rho_chns*U_ref_chns)/((etaT_chns+eta_chns)*48)))))
Failed_to_evaluate_symbolic_derivative_variable
Variable: shock_capt_chns@VDN${test@3}, Defined_as: ((r*(rho_chns*(-nojac(((min((ck_chns*sqrt((((taum_chns*res_v_chns)^2)+((((res_p_chns*tauc_chns)/(nojac(sqrt((u2int_g1_chns/vol_g1_chns)))*nojac((rhoint_g1_chns/vol_g1_chns)))))^2+((taum_chns*res_u_chns))^2)))),U_ref_chns)*0.5)*min((gijgij_chns^-0.25),((rho_chns*U_ref_chns)/((etaT_chns+eta_chns)*48))))))))*((ur*g21_chns)+(uz*g22_chns)))
Failed_to_evaluate_expression
Expression: d(((r*(-2*(eta_chns+etaT_chns)*ur+p)*test(ur)-r*(eta_chns+etaT_chns)*(uz+vr)*test(uz)+(-r*rho_chns*(u*ur+v*uz)-2*(eta_chns+etaT_chns)*u/r+p)*test(u)+gls_chns+shock_capt_chns)-(r*rho_chns*ut*test(u)))*(dvol),{test@3})
if someone could tell me on how to solve this probleme I will really appreciate.
best regards
Hello Soufiane Oukach
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Usually that means you need to add a constant somewhere in your expression, constant small enough not to alter the results and large enough never to let your expression go to zero so that the software can evaluate the inverse of the square root of the expression.
Can you give more details about the expressions you are using?
Hi ,
...
Time-dependent solver/Generalized alpha
Number of degrees of freedom solved for: 271446
Step Time Stepsize Res Jac Sol Order Tfail NLfail
0 0 out 3 2 2 0
Error:
Failed to find consistent initial values.
Sqrt_of_negative
Function: sqrt
Failed_to_evaluate_expression
Expression: nojac(((min((ck_chns*sqrt((((taum_chns*res_v_chns)^2)+((((res_p_chns*tauc_chns)/(nojac(sqrt((u2int_g1_chns/vol_g1_chns)))*nojac((rhoint_g1_chns/vol_g1_chns)))))^2+((taum_chns*res_u_chns))^2)))),U_ref_chns)*0.5)*min((gijgij_chns^-0.25),((rho_chns*U_ref_chns)/((etaT_chns+eta_chns)*48)))))
Failed_to_evaluate_symbolic_derivative_variable
Variable: shock_capt_chns@VDN${test@3}, Defined_as: ((r*(rho_chns*(-nojac(((min((ck_chns*sqrt((((taum_chns*res_v_chns)^2)+((((res_p_chns*tauc_chns)/(nojac(sqrt((u2int_g1_chns/vol_g1_chns)))*nojac((rhoint_g1_chns/vol_g1_chns)))))^2+((taum_chns*res_u_chns))^2)))),U_ref_chns)*0.5)*min((gijgij_chns^-0.25),((rho_chns*U_ref_chns)/((etaT_chns+eta_chns)*48))))))))*((ur*g21_chns)+(uz*g22_chns)))
Failed_to_evaluate_expression
Expression: d(((r*(-2*(eta_chns+etaT_chns)*ur+p)*test(ur)-r*(eta_chns+etaT_chns)*(uz+vr)*test(uz)+(-r*rho_chns*(u*ur+v*uz)-2*(eta_chns+etaT_chns)*u/r+p)*test(u)+gls_chns+shock_capt_chns)-(r*rho_chns*ut*test(u)))*(dvol),{test@3})
if someone could tell me on how to solve this probleme I will really appreciate.
best regards