A numerical study has been done on a rectangle in a 2D pipe flow. Therefore a Matlab code is made from scratch on basis of the SIMPLE algorithm. In the appendix is explained step by step exactly how all equations are implemented in Matlab. Focusing on low Reynolds numbers (1<Re<80) are different simulations made of the flow with the rectangle. Different heights of the rectangle in the pipe in a pressure driven flow are considered. Drag, lift and torque coefficients that were obtained from these simulations are plotted against the Reynolds number. Furthermore are shear flows as a consequence of a moving wall considered. Plots and other data of the dimensionless coefficients are included. The goal to make a good simulation of the flow past a rectangle is achieved. Different possible improvements to the code have been opposed, so it can be improved in the future to make also simulations of more complex geometries than a rectangle.