{"id":358065,"date":"2024-03-20T06:05:47","date_gmt":"2024-03-20T06:05:47","guid":{"rendered":"\/forum\/forums\/topic\/coupled-simulation-of-vehicle-and-fluid-tank-2\/"},"modified":"2024-03-20T06:05:47","modified_gmt":"2024-03-20T06:05:47","slug":"coupled-simulation-of-vehicle-and-fluid-tank-2","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/coupled-simulation-of-vehicle-and-fluid-tank-2\/","title":{"rendered":"coupled simulation of vehicle and fluid tank"},"content":{"rendered":"

Good morning sir\/mam,<\/p>\n

i am doing coupled simulation of vehicle and fluid tank thtough UDF using ansys fluent.  UDF is succesfully compliled but at the time of running simulation it showing bad termination of FFF fluent and automatically shut down. below is my UDF.  <\/p>\n

\n
#include “udf.h”<\/div>\n

<\/p>\n

DEFINE_ADJUST(coupled_simulation, d)<\/div>\n
{<\/div>\n
    real simulation_time = RP_Get_Real(“flow-time”);<\/div>\n
    real dt = 0.0001; \/\/ Time step size<\/div>\n
    real end_time = 15; \/\/ End time of simulation<\/div>\n

<\/p>\n

    Domain *domain = Get_Domain(2); \/\/ Assuming the fluid domain has ID 2<\/div>\n

<\/p>\n

    if (!domain)<\/div>\n
    {<\/div>\n
        Message(“Error: Unable to obtain domain.\\n”);<\/div>\n
        return;<\/div>\n
    }<\/div>\n

<\/p>\n

    \/\/ Define vehicle parameters<\/div>\n
    real m_truck = 5450.0; \/\/ Mass of the truck (kg)<\/div>\n
    real I_truck = 5000.0; \/\/ Moment of inertia of the truck (kg*m^2)<\/div>\n
    real k1 = 2.86e10; \/\/ Front spring stiffness (N\/m)<\/div>\n
    real k2 = 3.870e5; \/\/ Rear spring stiffness (N\/m)<\/div>\n
    real l1 = 0.2; \/\/ Distance of front axle from CG (m)<\/div>\n
    real l2 = 0.8; \/\/ Distance of rear axle from CG (m)<\/div>\n
    real F_braking = 1000.0; \/\/ Braking force (N)<\/div>\n

<\/p>\n

    \/\/ Define fluid parameters for water phase<\/div>\n
    real fluid_density_water = 1000.0; \/\/ Density of water (kg\/m^3)<\/div>\n

<\/p>\n

    \/\/ Define fluid parameters for air phase<\/div>\n
    real fluid_density_air = 1.2; \/\/ Density of air (kg\/m^3)<\/div>\n

<\/p>\n

    \/\/ Initial conditions for vehicle motion<\/div>\n
    real x = 1.0; \/\/ Initial vertical displacement<\/div>\n
    real theta = 1.0; \/\/ Initial angular displacement<\/div>\n
    real x_dot = 0.0; \/\/ Initial vertical velocity<\/div>\n
    real theta_dot = 0.0; \/\/ Initial angular velocity<\/div>\n
    real x_ddot = 0.0; \/\/vehicle acceleration<\/div>\n

<\/p>\n

    real fluid_force_x_water = 0.0, fluid_force_x_air = 0.0;<\/div>\n
    real fluid_force_y_water = 0.0, fluid_force_y_air = 0.0;<\/div>\n
    real fluid_force_z_water = 0.0, fluid_force_z_air = 0.0;<\/div>\n
    real fluid_moment_x_water = 0.0, fluid_moment_x_air = 0.0;<\/div>\n
    real fluid_moment_y_water = 0.0, fluid_moment_y_air = 0.0;<\/div>\n
    real fluid_moment_z_water = 0.0, fluid_moment_z_air = 0.0;<\/div>\n

<\/p>\n

    Thread *t;<\/div>\n
    face_t f;<\/div>\n
    cell_t c;<\/div>\n
   <\/div>\n
    \/\/ Main simulation loop<\/div>\n
    while (simulation_time < end_time)<\/div>\n
    {<\/div>\n
        \/\/ Step 1: Calculate vehicle response to braking force<\/div>\n
        real x_ddot = (-k1 * (x – l1 * theta) – k2 * (x + l2 * theta) + F_braking) \/ m_truck;<\/div>\n
        real theta_ddot = (-k1 * l1 * (x – l1 * theta) + k2 * l2 * (x + l2 * theta)) \/ I_truck;<\/div>\n
    \/\/ Step 2: Apply vehicle response to fluid domain as a body force in the source term<\/div>\n
    real vehicle_force_y = -m_truck * x_ddot;<\/div>\n
    real vehicle_moment_z = -k1 * l1 * (x – l1 * theta) + k2 * l2 * (x + l2 * theta);<\/div>\n
    \/\/ Loop over fluid cells<\/div>\n
    t = Lookup_Thread(domain, 2); \/\/ Assuming FLUID_THREAD_ID is the ID of the fluid thread<\/div>\n
    thread_loop_c(t, d)<\/div>\n
    {<\/div>\n
        begin_c_loop(c, t)<\/div>\n
        {<\/div>\n
            \/\/ Apply the body force components based on vehicle response<\/div>\n
            \/\/ For simplicity, assuming all the force acts in the y-direction<\/div>\n
            C_UDMI(c, t, 0) = 0.0; \/\/ Body force in x-direction<\/div>\n
            C_UDMI(c, t, 1) = vehicle_force_y; \/\/ Body force in y-direction<\/div>\n
            C_UDMI(c, t, 2) = 0.0; \/\/ Body force in z-direction<\/div>\n

<\/p>\n

            \/\/ Apply the moment components based on vehicle response<\/div>\n
            \/\/ Here, we’ll assume all the moments act around the z-axis<\/div>\n
            C_UDMI(c, t, 3) = 0.0; \/\/ Moment about x-axis<\/div>\n
            C_UDMI(c, t, 4) = 0.0; \/\/ Moment about y-axis<\/div>\n
            C_UDMI(c, t, 5) = vehicle_moment_z; \/\/ Moment about z-axis<\/div>\n
        }<\/div>\n
        end_c_loop(c, t);<\/div>\n
    }<\/div>\n

<\/p>\n

    \/\/ Step 3: Calculate fluid forces and moments for water and air phases<\/div>\n
    \/\/ Loop over fluid cells<\/div>\n
    t = Lookup_Thread(domain, 2); \/\/ Assuming FLUID_THREAD_ID is the ID of the fluid thread<\/div>\n
    thread_loop_c(t, d)<\/div>\n
    {<\/div>\n
        begin_c_loop(c, t)<\/div>\n
        {<\/div>\n
            real A[ND_ND], F[ND_ND], F_area[ND_ND]; \/\/ Add F_area vector to store face area<\/div>\n
            real p = C_P(c, t);                     \/\/ Pressure of the cell (initialise pressure value in Fluent= mg\/ base area)<\/div>\n
            C_CENTROID(A, c, t);                    \/\/ Centroid of the cell<\/div>\n

<\/p>\n

            for (int i = 0; i < ND_ND; i++)<\/div>\n
            {<\/div>\n
                F[i] = 0.0; \/\/ Initialize force vector<\/div>\n
            }<\/div>\n

<\/p>\n

            \/\/ Loop over faces of the cell using C_FACE macro<\/div>\n
            for (int f = 0; f < C_NFACES(c, t); f++)<\/div>\n
            {<\/div>\n
                face_t face = C_FACE(c, t, f);<\/div>\n
                F_AREA(F_area, face, t); \/\/ Face area vector<\/div>\n

<\/p>\n

                \/\/ Calculate face force<\/div>\n
                for (int j = 0; j < ND_ND; j++)<\/div>\n
                {<\/div>\n
                    F[j] += p * F_area[j]; \/\/ Use F_area instead of calling F_AREA macro multiple times<\/div>\n
                }<\/div>\n
            }<\/div>\n

<\/p>\n

            \/\/ Accumulate forces and moments for water phase<\/div>\n
            fluid_force_x_water += F[0];<\/div>\n
            fluid_force_y_water += F[1];<\/div>\n
            fluid_force_z_water += F[2];<\/div>\n
            fluid_moment_x_water += (A[1] * F[2] – A[2] * F[1]);<\/div>\n
            fluid_moment_y_water += (A[2] * F[0] – A[0] * F[2]);<\/div>\n
            fluid_moment_z_water += (A[0] * F[1] – A[1] * F[0]);<\/div>\n

<\/p>\n

            \/\/ Accumulate forces and moments for air phase<\/div>\n
            fluid_force_x_air += F[0];<\/div>\n
            fluid_force_y_air += F[1];<\/div>\n
            fluid_force_z_air += F[2];<\/div>\n
            fluid_moment_x_air += (A[1] * F[2] – A[2] * F[1]);<\/div>\n
            fluid_moment_y_air += (A[2] * F[0] – A[0] * F[2]);<\/div>\n
            fluid_moment_z_air += (A[0] * F[1] – A[1] * F[0]);<\/div>\n
        }<\/div>\n
        end_c_loop(c, t);<\/div>\n
    }<\/div>\n

<\/p>\n

    \/\/ Step 4: Update vehicle response based on fluid forces and moments as excitation force on vehicle equations<\/div>\n
    real fluid_force_x = fluid_force_x_water + fluid_force_x_air;<\/div>\n
    real fluid_force_y = fluid_force_y_water + fluid_force_y_air;<\/div>\n
    real fluid_force_z = fluid_force_z_water + fluid_force_z_air;<\/div>\n
     real fluid_moment_x = fluid_moment_x_water + fluid_moment_x_air;<\/div>\n
      real fluid_moment_y = fluid_moment_y_water + fluid_moment_y_air;<\/div>\n
       real fluid_moment_z = fluid_moment_z_water + fluid_moment_z_air;<\/div>\n

<\/p>\n

            x_dot += fluid_force_x \/ m_truck * dt;<\/div>\n
            theta_dot += fluid_moment_z \/ I_truck * dt;<\/div>\n

<\/p>\n

            x += x_dot * dt;<\/div>\n
         theta += theta_dot * dt;<\/div>\n
         \/\/ Increment simulation time<\/div>\n
        simulation_time += dt;<\/div>\n

<\/p>\n

         \/\/ Step 5: Output results if needed<\/div>\n
            printf(“Time: %.2f, x: %.4f, theta: %.4f\\n”, simulation_time, x, theta);<\/div>\n
            }<\/div>\n
   <\/div>\n<\/div>\n","protected":false},"template":"","class_list":["post-358065","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t