Cavity noise sensitivity analysis of tire contour design factors and application of contour optimization methodology

Cavity resonance noise of passenger car tires is generated by interacting excitation between a tire structure and the fill gas (air), and generally lies in a frequency range of 200?250 Hz. As such, this noise is strongly perceived and may be a serious source of driver annoyance. Thus, many studies regarding the cavity noise mechanism and its reduction have already been conducted. In this work, a vibro-acoustic coupled analysis was conducted between a tire structure and air cavity. Using this analysis, we can more accurately simulate the tire noise performance in the region of the cavity resonance frequency. An analysis of the effects of variation of tire contour design factors was conducted, using design-of-experiments methods. Finally, a multi-objective optimization was performed using in-house codes to reduce the cavity noise level while minimizing the loss of other performances, such as diminished ride comfort and handling caused by the variations of contour. As a result of this optimization, an optimized contour shape was derived, which satisfied the multi-objective performances.

An experimental study on thermal characteristics of nanofluid with graphene and multi-wall carbon nanotubes

High-thermal conductivity enhancement of nanofluid is one of the promising topics of the nanoscience research field. This work reports the experimental study on the preparation of graphene(GN) and multi-walled carbon nanotubes(MWCNTs) based nanofluids with the assistance of sodium dodecyl benzene sulfonate(SDBS) and sodium dodecyl sulfate(SDS) surfactants, and their thermal behaviors. The present work suggests not a solution, but a solution approach and deduces a new conclusion by trying to resolve the agglomeration problem and improve the dispersibility of nanoparticles in the base fluid. The analysis results of FESEM, thermal conductivity, diffusivity, effusivity and heat transfer coefficient enhancement ratio of nanofluid with surfactants SDS and SDBS expose strong evidence of the dispersing effect of surfactant on the making of nanofluid.

CFD analysis of sound pressure in tank gun muzzle silencer

The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems such as exposure of location of troops. This high pressure impulsive sound, generated during the blast flow, was studied and attenuated. An axisymmetric computational domain was constructed by employing Spalart Allmaras turbulence model. Approximately 90% of pressure and 20 dB of sound level are reduced due to the use of the three baffle silencer at the muzzle end of the gun barrel, in comparison with the tank gun without silencer. Also, the sound pressure level at different points in the ambient region shows the same attenuation in results. This study will be helpful to understand the blast wave characteristics and also to get a good idea to design silencer for large caliber weapon system.

Experimental assessment of two-phase bubble pump for solar water heating

The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat could be transferred downward from the collector to a hot water storage tank.The designed system consists of two sets of heat-pipe evacuated tube collectors,a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level.Discharge heads of 1 and 5 m were tested.The bubble pump could operate at the collector temperature of about 90-100 ℃ and vapor gage pressure of 80-90 kPa.It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head.Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly,daily and long-term performance tests.The thermal performance of the proposed system is compared with conventional solar water heaters.The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account.And the former is a zero carbon system.

Heat transfer characteristics of nanofluid through circular tube

Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.

Grinding Characteristic of Multi-walled Carbon Nanotubes-alumina Composite Particle

The synthesis of new materials containing multi-walled carbon nanotubes （MWCNTs） and the microstructure of alumina particles were investigated and characterized. The MWCNTs and alumina particles were ground under both the dry and wet conditions with various rotation speeds （200 - 400 r/min） in planetary ball milling machine, and their combination characteristics were described. The experimental results were examined by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, transmission electron microscopy （TEM） and particle sizing analysis （PSA）. SEM result revealed that the combination of MWCNTs - Alumina particles mixed quite well under both the dry and wet grinding with rotation speed of 400 r/rain. XRD characterization indicated the better result could get in ground samples at a rotation speed of 400 r/min. PSA result showed the particle size decreased with increase the grinding speeds. From the overall results, we observed that the grinding method can be used to synthesize new material with high efficiency.

Characterizing pressure fluctuation into single-loop oscillating heat pipe

The pressure characteristics inside single loop oscillating heat pipe(OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed.Distilled water was used as working fluid inside the OHP with different filling ratios of 40%,60% and 80% of total inside volume.Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency.And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60?96 °C.Piezoresistive absolute pressure sensor(Model-Kistler 4045A5) was used to take data.The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.

Liquid film falling behaviour on horizontal circular cylinder

The flow pattern behaviour of falling liquid film over three horizontal cylinders was evaluated.These flows can take three forms:discrete droplets,individual jets,and continuous sheet,and special attention is paid to the effects of the physical properties and geometrical parameters of the first two forms(droplets and jets) because these forms are more important in heat-transfer behaviour and less research has been published for these forms,The flow modes and experimental results were successfully compared with previous experimental literatures,and also the effects of liquid flow rate,tube diameter,and tube spacing on departure site spacing,in both drop and jet modes,were evaluated in the low Galileo number and high viscosity fluid(cooking oil),to help developing criteria for determining falling film modes and their transitions,and to understand the heat transfer characteristics associated with each mode.

Flow characteristics by particle image velocimetry in liquefied natural gas vaporizer model with several baffles

Shell-and-tube vaporizers are the most commonly used and dominated types of vaporizers in liquefied natural gas (LNG) realm.Due to efficient performance,shell-side flow in this type of vaporizers has received considerable attention and has been investigated extensively.However,the detailed flow structure in the shell needs to be determined for reliable and effective design.Therefore,the objective of this study was to clarify the flow structure in shell by particle image velocimetry (PIV).Experiments were conducted using two types of model;15% baffle cut having inlet and outlet positions in the direction of 90° to the cut and 30% baffle cut having inlet and outlet positions in the direction of 180° to the cut.Each test section is 169 mm in inner diameter and 344.6 mm in length.The flow features were characterized in different baffle cuts with regards to the velocity vector field and velocity distribution.The results show that the flow characteristics of 15% baffle cut type vaporizer are comparable to those of 30% baffle cut type vaporizer.

Pressure distribution inside oscillating heat pipe charged with aqueous Al_2O_3 nanoparticles,MWCNTs and their hybrid

Effective thermal performance of oscillating heat pipe(OHP)is driven by inside pressure distribution.Heat transfer phenomena were reported in terms of pressure and frequency of pressure fluctuation in multi loop OHP charged with aqueous Al2O3 and MWCNTs/Al2O3 nanoparticles.The influences on thermal resistance of aqueous Al2O3,MWCNTs as well as the hybrid of them in OHP having 3 mm in inner diameter were investigated at 60% filling ratio.Experimental results show that thermal characteristics are significantly inter-related with pressure distribution and strongly depend upon the number of pressure fluctuations with time.Frequency of pressure depends upon the power input in evaporative section.A little inclusion of MWCNTs into aqueous Al2O3 at 60% filling ratio achieves the highest fluctuation frequency and the lowest thermal resistance at any evaporator power input though different nanofluids cause different thermal performances of OHPs.

The Study on Effect of Exhaust Performance According to Active Muffler Valve Spring as Followed Spring Constant

This study represents the influence on exhaust performance by active muffler valve spring. The main experimental parameters were engine speeds and torsion coil spring constants in the active muffler. When the muffler valve spring has a low spring constant of k = 0.75, the sound pressure level was low at the region of engine speed 2000 to 2500 r/min, and the velocity of exhaust gas was high at spring constant k = 0.75. When the engine speed was under 1500 r/min, the mean concentration of CO was high in case without muffler valve. When the engine speed in the range of 1600 to 2600 r/min with spring constant k = 0.75, the mean HC concentration showed the lowest value. Without muffler valve, the temperature in the muffler was higher than the case with muffler valve. This research represented that the performance of the active muffler valve spring constant k = 0.75 was higher than that without muffler valve and valve spring constant k = 0.70. Among the three cases of experimental condition, with a spring

Beach stabilization by the laying of a drainage layer

In the present study,the stabilization effects of the laying of a drainage layer in a sandy beach were analyzed.The numerical model developed by Hur et al.(2011) was used to examine the characteristics of wave-sandy beach interaction with/without a drainage layer.This numerical model directly simulates Wave-Structure-Seabed/Sandy(WASS) beach interaction by considering flow through a porous medium with inertia,laminar and turbulent resistances,and determines the eddy viscosity with the Large Eddy Simulation(LES) turbulent model in a 3-D wave field(LES-WASS-3D).Based on the numerical results,it appears that the installation of a drainage layer in the beach results in a decrease in both the mean groundwater level around the foreshore and the flow moving offshore on the beach surface.Spatial distributions of the mean groundwater level and wave setup around the foreshore with various arrangements of the drainage layer and conditions of the incident wave are also discussed in this paper.