Bruce Jenkins, Ora Research
For CFD-driven shape optimization of water pumps with shrouded impellers, it’s essential to have an efficient variable-geometry model defined by a set of relevant parameters (design variables). This case-study example focuses on geometry modeling of a typical water pump, with the goal of attaining maximum flexibility in shape variation and fine-tuning.
To begin, the geometry was set up in CAESES (CAE System Empowering Simulation), the software platform from FRIENDSHIP SYSTEMS that helps engineers design optimal flow-exposed products. CAESES provides simulation-ready parametric CAD for complex free-form surfaces, and targets CFD-driven design processes. Its specialized geometry models are ideally suited to automated design exploration and shape optimization.
The animations shown below were generated in CAESES by varying all design variables simultaneously. The geometry variations in these animations are exaggerated to make clearly visible how the shape is being varied; in a real-world use case, the changes that engineers would make to their initial design would likely not be as large.
The hub and shroud contours, as well as the leading-edge curve, were designed in the Z-X-axis view. Variables were created and connected to these curves—for example, to the control vertices of the B-spline curves or to an angle control—so that they could be varied through the automated process of design exploration. The entire shape can also be controlled and adjusted manually based on engineering intuition, if needed.
Variation of meridional contours.
Blade camber and thickness
The camber surface of the blade was generated using a theta function in the (m,theta)-system. The function graph shown above is a 2D curve definition for which additional design variables were created and connected. From this function and from the leading-edge contour in the meridional plane, the camber surface was derived.
Theta function for generating camber surface.
Next a user-defined thickness distribution was applied normal to the generated camber surface. To control the shape, additional design variables were introduced to change the leading-edge region to be more elliptical than circular, and to vary thickness from leading edge to trailing edge. In addition, the thickness could be varied in the radial direction—that is, while sweeping from hub to shroud.
Variation of impeller blade.
Boolean operations and filleting
After the blade surface was generated, it was combined with the hub and shroud surfaces. CAESES’ Boolean operations were used to merge these geometries. Fillets were created at the intersection of the blade and the remaining geometry. The model shown above has two fillets: one between blade and hub, and another between blade and shroud. Below is an animation from the top view of the final impeller:
Water pump variation (top view).
And a final view, zoomed in:
Water pump variation (zoom).
Friendship Systems CAESES