Sheikh Ahmad Zaki Shaikh Salim

Downstream flat plate as the flow-induced vibration enhancer for energy harvesting

The prospect of harvesting energy from flow-induced vibration using an elastic square cylinder with a detached flat plate is experimentally investigated. The feasibility of flow-induced vibration to supply an adequate base excitation for micro-scale electrical power generation is assessed through a series of wind tunnel tests. The current test model of a single square cylinder is verified through a comparable pattern of vibration amplitude response with previous experimental study and two-dimensional numerical simulations based on the unsteady Reynolds averaged Navier–Stokes (URANS). In addition, a downstream flat plate is included in the wake of the square cylinder to study the effects of wake interference upon flow-induced vibration. A downstream flat plate is introduced as the passive vibration control to enhance the magnitude of flow-induced vibration and simultaneously increases the prospect of harvesting energy from the airflow. The study is conducted by varying the gap separation between the square cylinder and flat plate for 0.1≤ G/D ≤3. The highest peak amplitude is observed for the gap G/D = 1.2 with yrms/D = 0.46 at UR = 17, which is expected to harvest ten times more energy than the single square cylinder. The high amplitude vibration response is sustained within a relatively broader range of lock-in synchronization. Meanwhile, for G/D = 2 the vibration is suppressed, which leads to a lower magnitude of harvested energy. Contrarily, the amplitude response pattern for G/D = 3 is in agreement with the single square cylinder. Hence, the flat plate has no significance to the wake interference of the square cylinder when the gap separation is beyond 3D.

Aeolian Tones Radiated from Flow Over Bluff Bodies

Bluff body is a simple but a central shape for many engineering applications. The geometry shape of the bluff body characterises the behaviour of the flow over the bluff body, where a more complex flow structure is found near downstream. Shear layer separation is mainly responsible for the periodic global phenomena, that includes the generation of sound. The magnitude of the aerodynamically generated sound is dominated by the fluctuations of aerodynamics forces, i.e., drag and lift. The study also shows that the sound pressure field is shaped by the aeolian tones that is related strongly to the lift fluctuations of the bluff body. Amplitude and frequency of the fluctuating lift change naturally with the shape of a particular bluff body. Triangular cylinder exhibits the largest sound pressure level (41.9 dB) followed by ellipse and circular shapes. Square cylinder emits the lowest sound pressure level (36.7 dB). This corresponds to the longest downstream vortex formation length at which for a square cylinder the long vortex formation length provides space for more vortex to dissipate.

Numerical Simulation of Noise Radiated from a Blunt Trailing Edge

The Lighthill acoustic analogy is applied to estimate the noise radiation from flow over a blunt trailing edge. The blunt trailing edge is an effective vortex generator. Periodic vortex shedding near the trailing edge induces fluctuating lift that radiates a strong Aeolian tone. The frequency of the Aeolian tone is similar to that of the vortex shedding. A 50.1 dB of Aeolian tone level is radiated from this blunt trailing edge.

Enhancing Ride Comfort of Quarter Car Semi-active Suspension System Through State-Feedback Controller

The objective of this study is to simulate the road disturbance toward suspension in quarter car system. Suspension consists of the system of springs, shock absorbers, and linkages that connects a vehicle to its wheel and allows relative motion between the car body and the wheel. This paper shows the mathematical modeling in order to design the quarter car suspension system using Simulink and MATLAB software. The work shows the effect of suspension travel in quarter car system toward road profile by using state-feedback controller. The state-feedback controller’s purpose is to decrease the continuous damping in suspension system. The inconsistency condition of the road is the main element that affects the ride comfort which is in this paper represented by different heights of road profile. In suspension principles, the road wheels and vehicle body produce vertical forces which are rotational motions. Therefore, state-feedback controller must be able to reduce body deflection caused by road disturbance to achieve the ride comfort of driver and passengers. The results show that the proposed controller is capable of reducing the vibration of suspension after experiencing the bumps with different heights.

Performance Comparison of Controllers for Suppressing the Structural Building Vibration

Zarina Mohd Noh*, Abdul Rahman Ramli, Marsyita Hanafi, M Iqbal Saripan, Ridza Azri Ramlee 1,2,3,4 Department of Computer and Communication Systems Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia 1,5 Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, 75450 Durian Tunggal, Melaka, Malaysia

Numerical Simulation of Liquids Draining From a Tank Using OpenFOAM

Accurate simulation of liquids draining is a challenging task. It involves two phases flow, i.e. liquid and air. In this study draining a liquid from a cylindrical tank is numerically simulated using OpenFOAM. OpenFOAM is an open source CFD package and it becomes increasingly popular among the academician and also industries. Comparisons with theoretical and results from previous published data confirmed that OpenFOAM is able to simulate the liquids draining very well. This is done using the gas-liquid interface solver available in the standard library of OpenFOAM. Additionally, this study was also able to explain the physics flow of the draining tank.

Wind energy harvesting from wind-induced vibration

Wind power is a clean energy source and alternative to the non-renewable type of energy sources. One of the challenges in utilizing wind energy is to efficiently harvest the wind energy into a usable electrical power, especially in the regions with low wind speed. This study aims to assess the possibility of harvesting wind energy by using the concept of flow induced vibration of a bluff body. A thin flat plate is introduced downstream of the cylinder as a simple but effective passive wind control. Three conditions have been tested to evaluate its effects on wind energy harvesting: isolated cylinder, flat plate with vibrating cylinder and cylinder with vibrating flat plate. The wind-body interaction is simulated using mesh motion technique available in OpenFOAM, an open source code for Computational Fluid Dynamics, while the harvested energy is calculated based on the work done by the single degree of freedom (SDOF) vibrating body. The study found that the vibrating cylinder with flat plate harvests more energy than the isolated cylinder and the fixed cylinder with vibrating flat plate for a relatively wider range of wind speeds. This is due to the generated transverse force on the cylinder is higher than the transverse force generated on the flat plate. The highest energy produced by the vibrating cylinder with a flat plate is Pgen = 86.97 mW at reduced velocity, UR = 11, which is 4 times larger than for isolated cylinder with Pgen = 24.50 mW at UR = 20. For the case of a cylinder with vibrating flat plate, the energy produced is very small with Pgen = 0.6972 mW at UR = 10. The energy produced by the vibrating body is closely related not only to the wind velocity and vibration amplitude but also highly dependent on the rate at which the vibration occurs (frequency) and the phase difference between vibration and the generated force on the body. In the present study, the vibrating cylinder with flat plate appears to be the best configuration to harvest wind energy compared to the other configurations at reduced velocity UR = (9-11).

Study of Wake Profiles of a Simplified Model of High Speed Train Using RANS and LES Turbulent Models

Flow structure over bluff bodies is more complex in wake. The wake is characterized by the unsteady behavior of the flow, large scale turbulent structure and strong recirculation region. For the case of high speed train, wake can be observed at the gap between the coaches and also on the rear coach. Wakes formation of high speed train are generated by free shear layer that is originated from the flow separation due to the sudden change in geometry. RANS and LES turbulent models are used in this paper to stimulate the formation of wakes and behavior of the flow over a simplified high speed train model. This model consists of two coaches with the gap between them is 0.5D. A total of four simulations have been made to study the effect of computational domain size and grid resolution on wake profiles of a simplified high speed train. The result shows that the computational domain can be reduced by decreasing the ground distance to 1.5D without affecting the magnitude of the wake profile. Both RANS and LES can capture the formation of the wake, but LES requires further grid refinement as the results between the two grid resolutions are grid dependent.