3D音響解析

This example shows how to perform an acoustic analysis using PyMAPDL and FLUID elements.

Launch PyMAPDL

Launch PyMAPDL and load matplotlib.

from matplotlib import pyplot as plt

from ansys.mapdl.core import launch_mapdl

mapdl = launch_mapdl()

mapdl.clear()
mapdl.prep7()
mapdl.units("SI")  # SI - International system (m, kg, s, K).

Element and Material Properties

Define the FLUID30 and FLUID130 element types.

mapdl.et(1, "FLUID30", kop1=2)


# Define the material properties
mapdl.mp("SONC", 1, 1500)  # sonc in m/s
mapdl.mp("DENS", 1, 1000)  # Density in kg/m3
print(mapdl.mplist())


# Define the real const
mapdl.r("1", "1e-6")  # Reference pressure for R set 1
print(mapdl.rlist())

Geometry Definition

Create a simple sphere.

vnum = mapdl.sphere(rad1=0.5, rad2=1.0)
mapdl.vsbw("all")
mapdl.vplot(show_area_numbering=True)

Geometry Meshing

First select the material and elements.

mapdl.type(itype=1)
mapdl.real(nset=1)
mapdl.mat(mat=1)
mapdl.mshape(1, "3D")

Then choose the element size and perform the mesh.

mapdl.esize(0.25)
mapdl.vmesh("all")
mapdl.eplot(show_node_numbering=False)

Boundary Conditions

Add surface boundary condition to the nodes using Mapdl.sf() and the option SHLD for Surface normal velocity or acceleration.

mapdl.csys(2)
mapdl.asel("s", "loc", "x", 0.5)
mapdl.csys(0)
mapdl.nsla("S", 1)
mapdl.sf("all", "SHLD", 5)
mapdl.allsel()

Solve the model

Using Mapdl.solve()

mapdl.allsel()
mapdl.run("/SOLU")
mapdl.antype(3)
mapdl.harfrq(freqb=200, freqe=1000)
mapdl.autots("off")
mapdl.nsubst(40)
mapdl.kbc(0)

mapdl.outres("erase")  # Save less data in order to reduce the size of .rst file
mapdl.outres("all", "none")  # NOTE that other output like stresses is not saved
mapdl.outres("nsol", "all")  # Save pressure and displacement
mapdl.outres("fgrad", "all")  # Save velocities
mapdl.outres("misc", "all")  # For post processing calculations

mapdl.solve()

Post1: Time step results

Listing the results

mapdl.post1()
print(mapdl.set("LIST"))

Post26: Time dependent results

Getting results for specific nodes

mapdl.post26()
freqs = mapdl.post_processing.time_values[::2]
node = 276

# Getting results
node_pressure = mapdl.nsol(3, node, "spl")
node_sound_pressure_level = mapdl.nsol(4, node, "SPLA")

# Plotting
fig, ax = plt.subplots(1, 2)

ax[0].plot(freqs, node_pressure)
ax[0].set_xlabel("Frequencies (Hz)")
ax[0].set_ylabel("Sound pressure level (Pa)")

ax[1].plot(freqs, node_sound_pressure_level, label="Nodal Sound Pressure")
ax[1].set_xlabel("Frequencies (Hz)")
ax[1].set_ylabel("A-weighted sound\npressure level (dBA)")

fig.suptitle(f"Node {node} Results")
fig.tight_layout()
fig.show()

Stop MAPDL

mapdl.exit()