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