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Exhaust muffler system iscommonly used to reduce noise associated with internal combustion engine exhausts.This paper presents a numerical analysis of transmission loss for exhaust muffler by using transfer matrix method. The objective of this study is to develop the computer program to predict the transmission loss of muffler.The influence of cross sectional area of pipe, effect of muffler length and temperature towards the transmission loss of muffler is discussed as well in present study. The efficiency and capabilities of the computing transmission loss is compared to the experiment results obtained from the previous established research paper.

The proposed paper investigates experimentally the effectiveness of strakes in suppressing the vortex-induced vibration (VIV) of a long flexible cylinder by varying the pitch, height and the number of helix of the strakes, which differ from the previous studies that only focus on short rigid cylinder. The experiment was conducted in towing tank with constant velocity under subcritical Reynolds number () by using a Poly Vinyl Chloride cylinder with aspect ratio of 162. CCD cameras were installed to capture the amplitude vibration and the frequency responses in both in-line (IL) and cross-flow (CF) directions while the fluctuation of tension was measured by using tension load-cell. The theoretical laminar boundary layer thickness around a circular cylinder was calculated and was used as a benchmark in deciding the height of strakes for the experiment. The purpose of present study is to identify the optimum configuration of helical strakes that can be implemented on a long flexible riser with low mass ratio. The experimental result shows the helical strakes perform well in mitigating the VIV. Significant VIV mitigation is found for the strakes with a certain height which is larger than the laminar boundary layer thickness. However, its effectiveness in suppressing the vibration amplitude of flexible cylinder is far smaller than the rigid cylinder. Varying the pitch of strakes influents the occurrence of lock-in region and prevent the switch of frequency into higher mode. Previous study stated that pitch of 15D is as effective as 5D for a rigid cylinder. However, it does not work on a flexible cylinder. Changing the height of strakes narrows the lock-in region and contributes most in suppressing the vibration of cylinder. Also, it is surprising to find that two-helical strakes perform slightly better than three-helical strakes in lower velocity range. The hydrodynamic forces of cylinders are still in the process of analysing. The information presented in this paper will shed some light on the effectiveness of strakes with different configurations and suggest the appropriate dimension of strakes in term of pitch, height and the number of helix of the strakes as currently the available resources are limited.

Abstract. In the study, the vortex-induced vibration (VIV) of a cylinder fitted with and without helical strakes is investigated using fluid-structure interaction (FSI) software. The purpose is to predict the VIV characteristic of cylinder fitted with and without helical strakes. Fluid and structural solvers in commercial computational fluid dynamic (CFD) software were implemented as two-way FSI solvers to develop the simulation. A flexible circular cylinder of diameter, D = 0.018 m was tested. The pitch and height of the helical strakes were 10D and 0.10D, respectively. Existing experiment outputs of bare cylinder were used as benchmark to verify the simulated results. In overall, the simulation was able to predict the trend of the amplitude response and the mean drag coefficient. However, a slight over-prediction was noticed. It was also found that the helical strakes was able to reduce up to 60% of the VIV in water.

Guardrails are the most important road furniture which prevent vehicles from going off the road or into the opposite lane. It also protects objects at the roadside and prevent vehicles from entering into dangerous areas such a ravine or river. Performance of guardrails is not only influenced by their own design, but also the design of the vehicle. The design of guardrails is mostly aimed to reduce serious effects towards vehicles and users in an event of an accident. Bolster Barrier (BOLER) is an impact device that enhances the existing W-shape guardrails that are intended to reduce the accident impact between road users and the guardrails themselves. The application of BOLER is focused at critical areas. The purpose of this device is to reduce the numbers of serious injuries and fatalities in an accident. BOLER involved an impact test known as dolly test at MIROS Lab, Provisional CRASE Crash Centre (PC3) of Ayer Molek, Melaka. The test measured the dolly's velocity, W-beam guardrail bar's deformation and the overall force overtime trace. The results for standard the W-beam guardrail with new impact device showed a lower peak force (47.6kN versus 51.5kN) and a delay in reaching peak force by 11.4 milliseconds as compared to guardrails without the new guardrail device. This delay of 11.4 milliseconds is crucial allowing airbags to inflate before full impact.