interpolation of scattered Datas with concave boundary. contourf plot of scattered datas

Hello.

I want to plot my surface Solutions from Ansys Fluent in a contourf-Plot with Matlab. The Solution is a table in the ASCII-Format with scattered points (x,y,z) which decribe a plane and a temperature is given at each of those points.

On the first picture you can see a Scattered Plot with all Points and temperature-colored. Here you can see the correct geometry of the boundary.

But if I want a contourplot, I need to interpolate the scattered points. On the next picture you can see the result. The Problem is, that matlab interpolate "through" the boundary for example at the bottom. I think the problem has something to do with the "concave" boundary and the Delauney-Triangulation.

My Code

clear all
close all
clc

data_txt = importdata('file'); % 5Columns: NodeNumber, x,y,z,temperature

data_int = scatteredInterpolant(data_txt.data(:,3),data_txt.data(:,4),data_txt.data(:,5),'natural','none');

x_min=min(data_txt.data(:,2));
x_max=max(data_txt.data(:,2));

y_min=min(data_txt.data(:,3));
y_max=max(data_txt.data(:,3));

z_min=min(data_txt.data(:,4));
z_max=max(data_txt.data(:,4));

x = x_min:0.0001:x_max;
y = y_min:0.0001:y_max;
z = z_min:0.0001:z_max;

[Y, Z] = meshgrid(y, z);

data_int_ = data_int(Y,Z);

figure_handle=figure;
contourf(Y,Z,data_int_,100,'Edgecolor','none');

In this case, the x-Coodinate is constant. I can do this with every coordiante by using a Rotation-Matrix. Than I have a x,y,data problem.

Is there a way to interpoalte my scattered points, but to get my correct boundary shape? How can i stop Matlab to interpolate in regions, where no datas available?

Please help me!

[Arvind Narayanan]

Can you share the input data? Will help understand the behavior of the plot.