The occurrence and development of the dominant unsteady flow structures in a vanless centrifugal pump impeller are revealed by the Proper orthogonal decomposition (POD) method. The pressure and velocity data of four radial surfaces is selected as the variables of decomposition. The results show that this method is beneficial to the analysis of flow field when there is no strong interaction of flow structures. When the flow rate starts to decrease from the design flow rate, unstable flow phenomenon such as flow separation and wake begin to appear and develop in the impeller. The POD analysis reveals the influence of the main unsteady structures on the flow field when there is no mixed or have little interaction among flow structures. It outlines the development of flow separation near the suction side of impeller and the wake near the trailing edge as the flow rate changes. However, the flow field inside the impeller becomes more and more complex as the operation condition is far away from the design condition, which needs to be combined with other methods to better analyze the flow field.

This paper investigates the performance of a non-symmetric airfoil in a perturbed flow for a low Reynolds number by creating small vortical structures. A newly designed two-dimensional numerical tool is used to examine the interaction between the NACA 23015 airfoil and the vortex shedding from a square cylinder. Different airfoil position ratios are numerically simulated concerning the square cylinder G/D (D: square cylinder diameter), the channel centerline T/d (d=D/2), and the vortices scale size D/c (c: airfoil chord length). Results show that the maximum values of the lift and drag aerodynamic coefficients are influenced by the airfoil’s lateral and longitudinal positions. The Proper orthogonal decomposition (POD) method is used to identify the most energetic flow structures. For all simulated scenarios, it was found that the first two modes reflect the dominating coherent structures in the flow field. The results also show that a leading-edge vortex is formed over the airfoil. The observed phenomena of symmetric and antisymmetric shedding vortex mechanisms essentially depend on the lateral distance of the airfoil T/d and the vortex scale size D/c. However, the spectral analysis demonstrates that the shedding frequency mainly depends on the gap distance G/D.

This study deals with inverse approach for damage detection in a double-beam system. A double-beam system made of two parallel beams connected through an elastic layer. Degradation in stiffness of beams element, crack occurrence and partly destruction of inner layer has been considered as different types of damage. The time domain acceleration response of the system measured and Proper orthogonal decomposition has been applied to the collected data in order to derive the Proper orthogonal values (POV) and Proper orthogonal modes (POM) of the system. Effect of single damage in different locations on the POV has been analyzed and an objective function has been defined using the dominant POV and POM of each beam separately. In order to increase robustness of the method against noise, the objective function enriched by adding statistical Property of time domain response. The teaching-learning based optimization algorithm has been employed to solve optimization problem. Efficiency of the proposed method for detecting single and multiple damages in the system demonstrated with and without noise. Simulation results show good accuracy of the proposed method for detection single and multiple damages of different types in the system.

This paper presents the Large-Eddy-Simulation (LES) of two-phase turbulent thermo-magnetic convection of ferrofluid (water-Fe3O4) within a cubic cavity. The current two-phase model considers Brownian, thermophoresis, magnetophoresis, and eddy diffusions in the dispersion of ferromagnetic particles. Two parallel electrical wires influence ferrofluid flow. The numerical computations are performed by utilizing the finite volume method for three different magnetic numbers (i.e. Mnf=0, 1.4×1010 and 1.4×1010). For all numerical calculations, particle volume fraction and Rayleigh are held constant at 0.04 and 108, respectively. Based on the heat transfer analysis, a magnetic field with a strength of 5.6×1010 enhances the Nusselt number by 16.67%. Observed increases in heat transfer can probably be attributed to the Kelvin force induced by the magnetic field, which affects the coherent structures of the flow. Using the Proper orthogonal decomposition (POD) method, coherent structures are extracted from velocity and pressure fluctuations. Further, the time coefficients of the first three modes are extracted for the pressure fluctuation. According to the results, the applied magnetic field reduces the cumulative energy of modes and increases the number of modes required to reconstruct a given amount of flow. The coherent structures also change from plane to spanwise roll structures with increasing magnetic number. The energy content of the first three modes decreases from 98.7% to 73% as the magnetic field increases from Mnf=0 to 1.4×1010.