MATLAB讀取TECPLOT笛卡爾網格三維流場數據

基於笛卡爾網格的三維流動數值模擬，其流場信息可以通過tecplot格式進行輸出，方便tecplot對流場進行可視化處理，但對數據進行在加工時，還是導入matlab中比較方便，那么對於一個tecplot數據文件，matlab是不能直接讀取的，必須有一個函數將tecplot數據文件中數據轉換成matlab便於操作的數據格式。

tecplot數據文件前三行是文件頭，其中第一行是數據文件說明，第二行中是文件中所定義的變量名，第三行，對於笛卡爾網格的流場，其包含了每個空間方向上離散的數據數目。通過處理第二行文本，可以獲取所定義的變量及其數目。

tecplot文件中數據一行是一個記錄，一行中數據的順序和文件頭中第二行定義的變量順序相對應，通常前三個數據是x,y,z，對應網格點空間位置。

Title= "simulation data"
VARIABLES= "X","Y","Z","U","V","W","RHO"
ZONE T= "BOX",I= 100,J=321,K=100,F= POINT
0 0 0 0.000252868 0.00386761 -0.00194455 1000.01
1 0 0 -0.000252631 -0.00258331 0.00188909 1000.01
2 0 0 0.000252594 0.00441002 -0.00183506 1000.01
3 0 0 -0.000252256 -0.0019755 0.00178188 1000
4 0 0 0.000252931 0.00492305 -0.00173004 1000
...

1、matlab讀取tecplot文件，通過讀取文件頭獲取文件所定義變量以及變量數目，同時讀取文件中所包含數據信息，所讀取的數據保存在一個四維數組中，最后一個維度代表每個變量，變量名保存在一個元胞數組中。

1.1 tecplot數據為空間三維流場，tecplot2mat_3D

% read data from tecplot file, and save the variables to mat 
% filename: the name of the tecplot file including the extensions
% var: the data of variables, is a four dimensions array, the last dimension is the the number of variable
% var_name: the name of the variables, is a cell
% var_num: the number of the variables
function [var,var_name,var_num] = tecplot2mat_3D(filename)
%% tecplot data file read
% open the file
fid = fopen(filename);

% read the second line of data file
[~] = fgetl(fid);
str = fgetl(fid);

% get the number of the variables
o1 = regexpi(str,'"','start');
var_num = length(o1)/2;

% get the name of the variables
var_name = cell(1,var_num);
for i = 1:var_num
    var_name{1,i} = str(o1(2*i-1)+1:o1(2*i)-1);
end

% read the data
strformat = repmat('%f',1,var_num);
data = textscan(fid,strformat,'headerlines',1);
data = cell2mat(data);

% close the file
fclose(fid);

%% reshape data
% get discrete points
xi = sort(unique(data(:,1)));
yi = sort(unique(data(:,2)));
zi = sort(unique(data(:,3)));

% number of the discrete points
num_x = length(xi);
num_y = length(yi);
num_z = length(zi);

% initialize the three demonsions array
var = zeros(num_x,num_y,num_z,var_num);

% assignment the array according to the data
for n = 1:size(data,1)
    % method 1: we don't know the relationship between the number and the index, we must find the index according to the value    
    %     index_x = find( data(n,1) == xi );
    %     index_y = find( data(n,2) == yi );
    %     index_z = find( data(n,3) == zi );
    
    % method 2: we know the relationship between the value and the index, we can directly access the index 
    index_x = data(n,1) + 1;
    index_y = data(n,2) + 1;
    index_z = data(n,3) + 1;
    
    % access the data
    for i = 1:var_num
        var(index_x,index_y,index_z,i) = data(n,i);
    end
end

fprintf('reshape the data\n');

%% data save to mat
index_str = find( '.' == filename );
if isempty(index_str)
else
    filename = filename( 1:index_str-1 );
end
eval(['save ',filename,'.mat var var_name var_num;']);

fprintf('save the data\n');
end

1.2 tecplot數據為空間二維流場，tecplot2mat_2D

% read data from tecplot file, and save the variables to mat 
% filename: the name of the tecplot file including the extensions
% var: the data of variables, is a three dimensions array, the last dimension is the the number of variable
% var_name: the name of the variables, is a cell
% var_num: the number of the variables, is a number
function [var,var_name,var_num] = tecplot2mat_2D(filename)
%% tecplot data file read
% open the file
fid = fopen(filename);

% read the second line of data file 
[~] = fgetl(fid);
str = fgetl(fid);

% get the number of the variables
o1 = regexpi(str,'"','start');
var_num = length(o1)/2;

% get the name of the variables
var_name = cell(1,var_num);
for i = 1:var_num
    var_name{1,i} = str(o1(2*i-1)+1:o1(2*i)-1);
end

% read the data
strformat = repmat('%f',1,var_num);
data = textscan(fid,strformat,'headerlines',1);
data = cell2mat(data);

% close the file
fclose(fid);

%% reshape data
% get discrete points
xi = sort(unique(data(:,1)));
yi = sort(unique(data(:,2)));

% number of the discrete points
num_x = length(xi);
num_y = length(yi);

% initialize the three demonsions array
var = zeros(num_x,num_y,var_num);

% assignment the array according to the data
for n = 1:size(data,1)
    % method 1: we don't know the relationship between the number and the index, we must find the index according to the value
    %     index_x = find(data(n,1) == xi);
    %     index_y = find(data(n,2) == yi);
    
    % method 2: we know the relationship between the value and the index, we can directly access the index 
    index_x = data(n,1) + 1;
    index_y = data(n,2) + 1;
    
    % access the data
    for i = 1:var_num
        var(index_x,index_y,i) = data(n,i);
    end
end

fprintf('reshape the data\n');

%% data save to mat
index_str = find( '.' == filename );
if isempty(index_str)
else
    filename = filename( 1:index_str-1 );
end
eval(['save ',filename,'.mat var var_name var_num;']);

fprintf('save the data\n');
end

2、測試腳本，讀取給定的TECPLOT文件名，輸出文件包含數據以及將文件中定義的變量加載到MATLAB工作區

clc;clear;
close all;

filename = 'U3D.dat';
[var,var_name,var_num] = tecplot2mat_3D(filename);

for i = 1:var_num
    eval([var_name{1,i},'=var(:,:,:,i);']);
end

 3、測試結果，tecplot文件定義的變量就全部加載到工作區了。

 

 

備注:

采用上述腳本轉化的三維數組第一、二、三維度分別為x,y,z,而matlab中如想用這些三維數組數據做可視化圖像，需要采用y,x,z的次序組織數據，此時可以用permute函數對數據進行位置置換，范例如下：

X = permute( X, [ 2, 1, 3 ] )