GEOMETRICAL SOLID MODELING IS THE FIRST STEP IN FLOW SIMULATION WITHIN SOLID BOUNDARIES WITH COMPLEX OR UNKNOWN GEOMETRY. FOR COMPLEX ROTATING GEOMETRY SUCH AS TURBO PUMP IMPELLERS, ORDINARY MEASURING TOOLS CANNOT BE USED DIRECTLY DUE TO THE EXISTENCE OF COMPLEX CURVATURE AND ACUTE ANGLES. THEREFORE, A COMBINATION OF DIRECT MEASURING TOOLS SUCH AS VERNEAR, FRENCH CURVES AND INDIRECT MEASURING METHODS SUCH AS CASTING AND SOLID MODELING SOFTWARE MUST BE USED TO OBTAIN THE DIMENSIONS OF THE UNKNOWN BODY. IN THIS PAPER, A NEW PROCEDURE FOR OBTAINING COMPLEX GEOMETRY OF SOLID BODIES IS PRESENTED. AN INDUSTRIAL TURBO-PUMP IMPELLER THAT EMPLOYED IN BIDBOLAND GAS REFINERY HAS BEEN CHOSEN TO REPRESENT THE COMPLEX GEOMETRY. THE PROPOSED PROCEDURE IS BASED ON MAKING SMALL CHUCK CASTING FROM THE COMPLEX PASSAGES AND SIMULTANEOUSLY MAKING USE OF AVAILABLE COMPUTER AIDED DESIGN (CAD) SOFTWARE. DIMENSIONS OBTAINED FROM THE SMALL CASTS AND CURVE FITTING METHODS AND SIMULTANEOUSLY USING SOLID MODELING SOFTWARE GAVE THE COMPLETE UNKNOWN GEOMETRY.