You can model the repmat function used in the MATLAB function block above in Simulink as follows:
If the input array "u" has 2 dimensions feed it into a "Reshape" block. Set the output dimensionality to "Customize" and then set the output dimensions to: [1, XSize, YSize], where XSize and YSize are the dimension sizes of the original array. This will expand the third dimension. Then feed the output of the reshape block into a "Selector" block. Set the number of input dimensions to 3. Then for the first dimension set the index option to "Index vector (dialog)" and set the index value to "ones(1, Ns)". For the other two dimensions set the index option to "Select all".
Hope this helps.