  This article is concerned with the reconstruction of obstacle $\O$ immersed
in a fluid flowing in a bounded domain $\Omega$ in the two dimensional case. We
assume that the fluid motion is governed by the Stokes-Brinkmann equations. We
make an internal measurement and then have a least-square approach to locate
the obstacle. The idea is to rewrite the reconstruction problem as a topology
optimization problem. The existence and the stability of the optimization
problem are demonstrated. We use here the concept of the topological gradient
in order to determine the obstacle and it's rough location. The topological
gradient is computed using a straightforward way based on a penalization
technique without the truncation method used in the literature. The unknown
obstacle is reconstructed using a level-set curve of the topological gradient.
Finally, we make some numerical examples exploring the efficiency of the
method.
