Regarding the ValueError

[Ritik Dubey]

Hey Dedalus users,

I was trying to simulate a modified vorticity equation, but I am facing some problems.

I have attached the complete script and the error message, please check it.

Why is this happening and how to resolve it?

"""
2D IVP problem,
simulating modified form of Vorticity equation,
              dt(curl(u)) - Dlap(curl(u))  + F = - (u.grad)curl(u)
              where,
                    u= velocity field
                    D= diffusion coeff. = viscosity/density
                    F= forcing
               
initial condition : u(t=0)=f(x)

"""

import numpy as np
import matplotlib.pyplot as plt
import dedalus.public as d3
import logging
logger = logging.getLogger(__name__)


# Parameters
Lx,Ly = 1,10
Nx,Ny = 100,100
dealias = 3/2
stop_sim_time = 100
timestepper = d3.RK222
timestep = 0.01
dtype = np.float64

# Bases
coord = d3.CartesianCoordinates('x','y')
dist = d3.Distributor(coord, dtype=dtype)
xbasis = d3.RealFourier(coord['x'], size=Nx, bounds=(0, Lx), dealias=dealias)
ybasis = d3.RealFourier(coord['y'], size=Ny, bounds=(0, Ly), dealias=dealias)


# Fields
u = dist.VectorField(coord, name='u',bases=(xbasis,ybasis))


# Substitutions
D=1

# Initial conditions
x = dist.local_grid(xbasis)
y=dist.local_grid(ybasis)
u['g'][0]= np.sin(np.pi*x/Lx)
u['g'][1]=np.cos(np.pi*y/Ly)
F=2*np.sin(x)*np.cos(y)


# Problem
problem = d3.IVP([u], namespace=locals())
problem.add_equation("dt(skew(u)) - D*lap(skew(u)) + F = - u@grad(skew(u)) ")


# Solver
solver = problem.build_solver(timestepper)
solver.stop_sim_time = stop_sim_time

# Main loop
u.change_scales(1)
u_list = []
t_list = []
while solver.proceed:
    solver.step(timestep)
    if solver.iteration % 100 == 0:
        logger.info('Iteration=%i, Time=%e, dt=%e' %(solver.iteration, solver.sim_time, timestep))
    if solver.iteration % 25 == 0:
        u.change_scales(1)
        u_list.append(np.copy(u['g']))
        t_list.append(solver.sim_time)


OUTPUT:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Regards,

--

Ritik Dubey

Indian Institute of Science Education and Research, Kolkata

Mohanpur, West Bengal - 741246