Tutorial: 2D Cylindrical Wave
From openEMS
- Download the latest matlab file using gitweb: CylindricalWave_CC.m
- Simulation Time: ~ 20 min
We will cover in this tutorial:
- setup a cylindrical mesh including five nested sub-grids
- define vtk and hdf5 dumps
- read, evaluate and visualize dumped field data with matlab
First Steps
- Install and verify your openEMS installation: Tutorial: First Steps
Matlab Simulation Script
- Start the script within an empty environment:
close all clear clc
- Setup basic simulation parameter
physical_constants mesh_res = 10; radius = 2560; split = ['80,160,320,640,1280']; split_N = 5; heigth = mesh_res*4; f0 = 1e9; exite_offset = 1300; excite_angle = 45;
- Cylindrical FDTD setup
FDTD = InitFDTD(100000,1e-4,'CoordSystem',1,'MultiGrid',split); FDTD = SetGaussExcite(FDTD,f0,f0/2); BC = [0 3 0 0 0 0]; % pml in positive r-direction FDTD = SetBoundaryCond(FDTD,BC);
- Setup the cylindrical mesh
% 50 mesh lines for the inner most mesh % increase the total number of meshlines in alpha direcion for all sub-grids N_alpha = 50 * 2^split_N + 1; CSX = InitCSX('CoordSystem',1); mesh.r = SmoothMeshLines([0 radius],mesh_res); mesh.a = linspace(-pi,pi,N_alpha); mesh.z = SmoothMeshLines([-heigth/2 0 heigth/2],mesh_res); CSX = DefineRectGrid(CSX, 1e-3,mesh);
- Setup an off-center excitation
start = [exite_offset excite_angle/180*pi-0.01 -20]; stop = [exite_offset excite_angle/180*pi+0.01 20]; CSX = AddExcitation(CSX,'excite',1,[0 0 1]); CSX = AddBox(CSX,'excite',0 ,start,stop);
- Define the dump boxes
start = [mesh.r(1) mesh.a(1) 0]; stop = [mesh.r(end-8) mesh.a(end) 0]; % time domain vtk dump CSX = AddDump(CSX,'Et_ra','DumpType',0,'FileType',0,'SubSampling','4,10,1'); CSX = AddBox(CSX,'Et_ra',0 , start,stop); % frequency domain hdf5 dump CSX = AddDump(CSX,'Ef_ra','DumpType',10,'FileType',1,'SubSampling','2,2,2','Frequency',f0); CSX = AddBox(CSX,'Ef_ra',0 , start,stop);
- Create the simulation folder/ write the xml file and run openEMS
Sim_Path = 'tmp'; Sim_CSX = '2D_CC_Wave.xml'; [status, message, messageid] = rmdir( Sim_Path, 's' ); % clear previous directory [status, message, messageid] = mkdir( Sim_Path ); % create empty simulation folder WriteOpenEMS([Sim_Path '/' Sim_CSX],FDTD,CSX); RunOpenEMS(Sim_Path, Sim_CSX);
- Visualize the field in the frequency domain as defined in the dump box
[field mesh_h5] = ReadHDF5Dump([Sim_Path '/Ef_ra.h5']); r = mesh_h5.lines{1}; a = mesh_h5.lines{2}; a(end+1) = a(1); %closeup mesh for visualization [R A] = ndgrid(r,a); X = R.*cos(A); Y = R.*sin(A); Ez = squeeze(field.FD.values{1}(:,:,1,3)); Ez(:,end+1) = Ez(:,1); %closeup mesh for visualization E_max = max(max(abs(Ez))); %get maximum E_z amplitude while 1 for ph = linspace(0,360,41) %animate phase from 0..360 degree surf(X,Y,real(Ez*exp(1j*ph*pi/180)),'EdgeColor','none') caxis([-E_max E_max]/10) zlim([-E_max E_max]) pause(0.3) end end
E_z(f) animation
