{"id":358956,"date":"2024-03-26T08:15:23","date_gmt":"2024-03-26T08:15:23","guid":{"rendered":"\/forum\/forums\/reply\/358956\/"},"modified":"2024-03-26T08:15:23","modified_gmt":"2024-03-26T08:15:23","slug":"358956","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/358956\/","title":{"rendered":"Reply To: coupled simulation of vehicle and fluid tank"},"content":{"rendered":"

<div><div>#include “udf.h”<\/div><div>#include <stdio.h> \/\/ Include the standard I\/O library for file operations<\/div><div>DEFINE_ADJUST(coupled_simulation1, d)<\/div><div>{<\/div><div>    real simulation_time = CURRENT_TIME; \/\/ Get the current simulation time<\/div><div>    real dt = RP_Get_Real(“flow-time-step”); \/\/ Get the flow time step<\/div><div>    real end_time = RP_Get_Real(“flow-time-end”); \/\/ End time of simulation<\/div><div>    real braking_duration = 2.0; \/\/ Duration of braking force (seconds)<\/div><div>    \/\/ Open file for writing<\/div><div>    FILE *fp;<\/div><div>    fp = fopen(“E:\\coupled trial 3\\50 prcnt_files\\dp0\\FFF\\Fluent\\libudf6\\result\\simulation_results.txt”, “w”);<\/div><div>    if (fp == NULL) \/\/ Check if file was opened successfully<\/div><div>    {<\/div><div>        Message(“Error opening file.\\n”);<\/div><div>        return -1; \/\/ Exit initialization function<\/div><div>    }<\/div><br><div>    Domain *domain = Get_Domain(3); \/\/ Replace 1 with the appropriate domain ID<\/div><br><div>    if (!domain)<\/div><div>    {<\/div><div>        Message(“Error: Unable to obtain domain.\\n”);<\/div><div>        fclose(fp); \/\/ Close the file before returning<\/div><div>        return -1; \/\/ Exit initialization function<\/div><div>    }<\/div><br><div>    \/\/ Define vehicle parameters<\/div><div>    real m_truck = 5450.0; \/\/ Mass of the truck (kg)<\/div><div>    real I_truck = 5000.0; \/\/ Moment of inertia of the truck (kg*m^2)<\/div><div>    real k1 = 2.86e10; \/\/ Front spring stiffness (N\/m)<\/div><div>    real k2 = 3.870e5; \/\/ Rear spring stiffness (N\/m)<\/div><div>    real l1 = 0.2; \/\/ Distance of front axle from CG (m)<\/div><div>    real l2 = 0.8; \/\/ Distance of rear axle from CG (m)<\/div><div>    real F_braking = 27000.0; \/\/ Braking force (N)<\/div><br><div>    \/\/ Define fluid parameters<\/div><div>    real fluid_density = 1000.0; \/\/ Density of the fluid (kg\/m^3)<\/div><br><div>    \/\/ Initial conditions for vehicle motion<\/div><div>    real x = 2.0; \/\/ Initial vertical displacement<\/div><div>    real theta = 2.0; \/\/ Initial angular displacement<\/div><div>    real x_dot = 0.0; \/\/ Initial vertical velocity<\/div><div>    real theta_dot = 0.0; \/\/ Initial angular velocity<\/div><br><div>    real fluid_force_x, fluid_force_y, fluid_force_z, fluid_moment_x, fluid_moment_y, fluid_moment_z;<\/div><br><div>    Thread *t;<\/div><div>    cell_t c;<\/div><div>    face_t f;<\/div><br><div>    \/\/ Main simulation loop<\/div><div>    while (simulation_time < end_time)<\/div><div>    {<\/div><div>        \/\/ Step 1: Calculate vehicle response to braking force<\/div><div>        real F_brake = (simulation_time < braking_duration) ? F_braking : 0.0; \/\/ Apply braking force only within the braking duration<\/div><div>        real x_ddot = (-k1 * (x – l1 * theta) – k2 * (x + l2 * theta) + F_braking) \/ m_truck;<\/div><div>        real theta_ddot = (-k1 * l1 * (x – l1 * theta) + k2 * l2 * (x + l2 * theta)) \/ I_truck;<\/div><br><div>        \/\/ Step 2: Apply vehicle response in terms of x(t) and theta(t) to fluid domain as a body force in the source term<\/div><div>        real vehicle_force_x = 0.0; \/\/ Body force in x-direction    <\/div><div>        real vehicle_force_y = 0.0; \/\/ Body force in y-direction<\/div><div>        real vehicle_force_z = 0.0;  \/\/ Body force in z-direction<\/div><div>        real vehicle_moment_x = 0.0; \/\/ vehicle moment in x-direction<\/div><div>        real vehicle_moment_y = 0.0; \/\/ vehicle moment in y-direction<\/div><div>        real vehicle_moment_z = 0.0; \/\/ vehicle moment in z-direction<\/div><div>        \/\/ Update the body force components based on vehicle response<\/div><div>        \/\/ For simplicity, assuming all the force acts in the z-direction<\/div><div>        vehicle_force_y = -m_truck * x_ddot;<\/div><div>        vehicle_moment_z = -k1 * l1 * (x – l1 * theta) + k2 * l2 * (x + l2 * theta);<\/div><div>        \/\/ Apply the body force to the fluid domain<\/div><div>        t = Lookup_Thread(domain, 3); \/\/ Assuming FLUID_THREAD_ID is the ID of the fluid thread<\/div><div>        thread_loop_c(t, d)<\/div><div>        {<\/div><div>            C_UDMI(c, t, 0) = vehicle_force_x;<\/div><div>            C_UDMI(c, t, 1) = vehicle_force_y;<\/div><div>            C_UDMI(c, t, 2) = vehicle_force_z;<\/div><div>           <\/div><div>             \/\/ Apply the moment components based on vehicle response<\/div><div>            \/\/ Here, we’ll assume all the moments act around the z-axis<\/div><div>            C_UDMI(c, t, 3) = 0.0; \/\/ Moment about x-axis<\/div><div>            C_UDMI(c, t, 4) = 0.0; \/\/ Moment about y-axis<\/div><div>            C_UDMI(c, t, 5) = vehicle_moment_z; \/\/ Moment about z-axis<\/div><div>        }<\/div><br><div>        \/\/ Step 3: Calculate fluid forces and moments<\/div><div>        fluid_force_x = 0.0;<\/div><div>        fluid_force_y = 0.0;<\/div><div>        fluid_force_z = 0.0;<\/div><div>        fluid_moment_x = 0.0;<\/div><div>        fluid_moment_y = 0.0;<\/div><div>        fluid_moment_z = 0.0;<\/div><br><div>        \/\/ Loop over fluid cells<\/div><div>        thread_loop_c(t, d)<\/div><div>        {<\/div><div>            begin_c_loop(c, t)<\/div><div>            {<\/div><div>                real A[ND_ND], F[ND_ND], F_area[ND_ND];  \/\/ Add F_area vector to store face area<\/div><div>                real p = C_P(c, t); \/\/ Pressure of the cell<\/div><div>                C_CENTROID(A, c, t); \/\/ Centroid of the cell<\/div><br><div>                for (int i = 0; i < ND_ND; i++)<\/div><div>                {<\/div><div>                    F[i] = 0.0; \/\/ Initialize force vector<\/div><div>                }<\/div><br><div>                \/\/ Loop over faces of the cell using C_FACE macro<\/div><div>                for (int f = 0; f < C_NFACES(c, t); f++)<\/div><div>                {<\/div><div>                    face_t face = C_FACE(c, t, f);<\/div><div>                    F_AREA(F_area, face, t); \/\/ Face area vector<\/div><br><div>                    \/\/ Calculate face force<\/div><div>                    for (int j = 0; j < ND_ND; j++)<\/div><div>                    {<\/div><div>                        F[j] += p * F_area[j]; \/\/ Use F_area instead of calling F_AREA macro multiple times<\/div><div>                    }<\/div><div>                }<\/div><br><div>                \/\/ Accumulate forces and moments<\/div><div>                fluid_force_x += F[0];<\/div><div>                fluid_force_y += F[1];<\/div><div>                fluid_force_z += F[2];<\/div><div>                fluid_moment_x += (A[1] * F[2] – A[2] * F[1]);<\/div><div>                fluid_moment_y += (A[2] * F[0] – A[0] * F[2]);<\/div><div>                fluid_moment_z += (A[0] * F[1] – A[1] * F[0]);<\/div><div>            }<\/div><div>            end_c_loop(c, t);<\/div><div>        }<\/div><br><div>        \/\/ Step 4: Update vehicle response based on fluid forces and moments as excitation force on vehicle equations<\/div><div>        x_dot += fluid_force_y \/ m_truck * dt;<\/div><div>        theta_dot += fluid_moment_z \/ I_truck * dt;<\/div><br><div>        x += x_dot * dt;<\/div><div>        theta += theta_dot * dt;<\/div><div>        \/\/ Update simulation results in the file<\/div><div>        fprintf(fp, “%.4f, %.4f\\n”, x, theta);<\/div><div>       <\/div><div>        printf(“Time: %.2f, x: %.4f, theta: %.4f\\n”, simulation_time, x, theta);<\/div><div>        \/\/ Increment simulation time<\/div><div>        simulation_time += dt;<\/div><div>    }<\/div><div>    \/\/ Close the file after simulation<\/div><div>    fclose(fp);<\/div><div>    return 0; \/\/ Successful initialization<\/div><div>}<\/div>now this code is getting compiled and hooking, but during simulation i am getting very low value of force in order of 0.4 N. i have doubt regarding macro i have used. could you please suggest me use of define_adjust macro is suitable for this coupled simulation or not??<\/div><\/p>\n","protected":false},"template":"","class_list":["post-358956","reply","type-reply","status-publish","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