Thoracic aortic aneurysm (TAA) is a severe cardiovascular disease with a high mortality rate, if left untreated. Clinical observations show that aneurysm growth can be linked to undesirable hemodynamic conditions of the aortic aneurysm. In order to gain more insight on TAA formation, we developed a computational framework in vitro to investigate and compare the flow patterns between pre-aneurismal and post-aneurismal aorta using a deformable wall model. This numerical framework was validated by an in vitro experiment accounting for the patient-specific geometrical features and the physiological conditions. The complex flow behaviors in the pre-aneurismal and post-aneurismal aorta were evaluated experimentally by particle image velocimetry (PIV). Our experimental results demonstrated flow behaviors similar to those observed in the fluid-structure interaction (FSI) numerical study. We observed a small vortex induced by the non-planarity of pre-aneurismal aorta near the aortic arch in pre-aneurysmal aorta may explain the aneurysm formation at the aortic arch. We found that high endothelial cell action potential (ECAP) correlates with the recirculation regions, which might indicate possible thrombus development. The promising image-based fluid-structure interaction model, accompanied with an in vitro experimental study, has the potential to be used for performing virtual implantation of newly developed stent graft for treatment of TAA.