Offices: The Netherlands Leeghwaterstraat 21 2628 CA Delft Tel.: +31 15 278 2907 Germany Weenermoorer Str. 193 26826 Weener Tel.: +49 4953 922 969 Consultancy for Heat Transfer and Fluid Dynamics We solve every Flow problem. In the world’s engine cooling and heating and ventilation markets the Multi-Wing brand  has established a powerful reputation for quality, performance, durability and effi-  ciency. Multi-Wing’s goal is to maintain and build upon that reputation through the  continued development of the Multi-Wing brand worldwide. Like any successful com-  pany, Multi-Wing’s impellers have been copied, but only genuine Multi-Wing products  produced by Multi-Wing International as carry the guarantee of performance, durability  and efficiency. As the inventor of the thermo plastic component impeller, Multi-Wing is  recognised as the world leader in axial fan impeller design and production. And, whilst  the product range has expanded considerably, the basic product concept remains –  producing highly efficient impellers from interchangeable components. Indeed, over  the last ten years, the company has discontinued all the other products it manu-  factured to concentrate on the development of Multi-Wing.   In 1997 FlowMotion designed with great success its first impeller. The design process  was based on methods which were  state of the art for that period. Since  then a lot has changed. The  introduction of CFD made it possible  to analyse and design fans and air  foils and CFD gave a very detailed  view of the aerodynamics. In the past  FlowMotion has used CFD with  success in the axial fan industry. The  final challenge for FlowMotion was to  create a mesh with the highest  quality possible. Together with Multi-  Wing an impeller has been selected to take on this challenge.   In order to create a mesh of such high quality the physical aspects of the flow  must be known. The boundary layer height is one of the most important aspects  of the flow around an airfoil. In order the achieve the correct y+ values a lot of  work has been put in the development of the boundary layer mesh. The  pressure distribution in the picture above shows the very thin boundary layer.  The gradients in a flow around a fast rotating fan can be quite large. The mesh  distribution is adapted to these gradients. Especially in the area of the tip  clearance a highly sophisticated mesh has been modelled.  Several points of the performance graph are calculated and compared with experiments. As can be seen in the graph  below a very good agreement is achieved, even in the higher pressure region. These latest developments can help  Multi-Wing in the development of new impellers.  One for all Design of an axial flow fan for many applications Multi-Wing International www.multi-wing.com 3D calculation grid of the blade and the diffusor Pressure distribution boundary layer pressure flowrate