Optimization of Hydraulic Machinery Bladings by Multilevel CFD Techniques

• Main Authors: Thum Susanne, Schilling Rudolf
• Format: Article
• Language: English
• Published: Hindawi Limited 2005-01-01
• Series: International Journal of Rotating Machinery
• Online Access: http://www.hindawi.net/access/get.aspx?journal=ijrm&volume=2005&pii=S1023621X02505029

<p>The numerical design optimization for complex hydraulic machinery bladings requires a high number of design parameters and the use of a precise CFD solver yielding high computational costs. To reduce the CPU time needed, a multilevel CFD method has been developed. First of all, the 3D blade geometry is parametrized by means of a geometric design tool to reduce the number of design parameters. To keep geometric accuracy, a special B-spline modification technique has been developed. On the first optimization level, a quasi-3D Euler code (EQ3D) is applied. To guarantee a sufficiently accurate result, the code is calibrated by a Navier-Stokes recalculation of the initial design and can be recalibrated after a number of optimization steps by another Navier-Stokes computation. After having got a convergent solution, the optimization process is repeated on the second level using a full 3D Euler code yielding a more accurate flow prediction. Finally, a 3D Navier-Stokes code is applied on the third level to search for the optimum optimorum by means of a fine-tuning of the geometrical parameters. To show the potential of the developed optimization system, the runner blading of a water turbine having a specific speed <math alttext="$n_{q}=41$"><msub><mi>n</mi> <mi>q</mi> </msub> <mo>=</mo> <mn>41</mn> </math> <math alttext="un{1/min}"><mrow><mn>1</mn> <mo>/</mo> <mrow><mtext>min</mtext> </mrow> </mrow> </math> was optimized applying the multilevel approach.</p>