Numerical studies on unsteady helicopter main-rotor-hub assembly wake

The objective of this research is to quantify viscous unsteady flow phenomenon observed behind a helicopter main-rotor-hub assembly, as the part is believed to be a major contributor to tail shake phenomenon. In this numerical investigation, the aerodynamic flow field was computed using Large Eddy Simulation equations. To simulate the wake dynamics, Multiple Reference Frames (MRF) method was applied to rotate the main-rotor-hub assembly. Simulations were also run with fairing installed on the main-rotor-hub assembly. The results concluded that fairing does significantly alter the wake's structures and help to reduce aerodynamic drag to about 5% lesser. In addition, analysis from power spectral density (PSD) had successfully quantified the frequencies of this unsteady wake, as well the strength of their amplitudes. It had also manifested a significant growth of wake amplitude to 109% when the rotor rotation was increased from 1400 rpm to 1600 rpm, implying a strong correlation between the flow unsteadiness and the speed of rotor rotation. These findings are alleged to be valuable for future research and development in the rotorcraft industry

Computational fluid dynamic (CFD) analysis of parachute canopies design for aludra SR-10 UAV as a parachute recovery systems (PRS)

Unmanned Systems Technology (UST) Aludra SR-10 Unmanned Aerial Vehicle (UAV) was purposely designed for survey and mapping mission. In the early design stage of Aludra SR-10 UAV, skid and belly landing method was used as a recovery method. This type of landing method may encounter a harsh landing on hard soil and gravel, producing high impact momentum on the aircraft body and may cause structural or system damage. To increase the safety of Aludra SR-10 UAV operation, Parachute Recovery System (PRS) are purposely design to replace the belly landing technique for landing method. This study was performed by simulation approach (using Computational Fluid Dynamic, CFD) to analyse an aerodynamic performance for selecting the best canopy design that can produce higher drag during recovery process. This computational study focuses on an aerodynamic flow simulation over threedimensional surface on two different canopy designs (i.e. annular canopy and cruciform canopy), and also focuses on drag coefficient in a steady and turbulent condition. Two‐equation k-ε turbulence flow was modelled by adopting Navier-Stokes numerical equations to simulate aerodynamic characteristics and drag. The computational results with an efficient grid study shows an annular parachute canopy produced highest drag coefficient (1.03) than cruciform parachute canopy (0.91). The findings also highlighted the significance of separation and recirculating flows behind studied geometries, which in turn was responsible in producing the drag. This computational simulation analysis successfully provided a baseline annular parachute design was about 2.41 meter of the nominal diameter was selected as the main parachute which can be applied for this research

Properties of zinc tin oxide thin film by aerosol assisted chemical vapor deposition (AACVD)

This study focuses on the properties of ZTO which have been deposited by a low-cost method namely aerosol assisted chemical vapor deposition (AACVD). The precursors used in this method were zinc acetate dihidrate and tin chloride dihydrate for ZTO thin film deposition. Both precursors were mixed and stirred until fully dissolved before deposition. The ZTO was deposited on borosilicate glass substrate for the investigation of optical properties. The films deposited have passed the scotch tape adherence test. XRD revealed that the crystal ZTO is slightly in the form of perovskite structure but several deteriorations were also seen in the spectrum. The UV-Vis analysis showed high transmittance of ∼85% and the band gap was calculated to be 3.85 eV. The average thickness of the film is around 284 nm. The results showed that the ZTO thin films have been successfully deposited by the utilization of AACVD method

Numerical simulation and wind tunnel measurements of lateral aerodynamic characteristics on simplified automotive model

Computational Fluid Dynamic (CFD) has become an important tool to solve various engineering problems related to aerodynamics. One such growing interest in CFD is to correlate results between CFD and wind tunnel tests. The accuracy of CFD has improved considerably over the years but still large errors are present and lateral aerodynamic characteristics such as drag, side force and yaw moment due to yaw angle are often poorly predicted especially on bluff body shapes. Due to this, comparison between CFD and wind tunnel measurements has become more on demand. The main goal of this research is to investigate the capability of CFD to determine aerodynamic characteristics of simple automotive type bodies and its effect on crosswind stability. An investigation was performed both experimentally and computationally to analyze the main characteristics of flow past a 1:6 scale wind tunnel model of a simplified automotive body shape with different rear slant angles. The investigations were focused on the prediction and measurement of drag, side force, yawing moment and flow characteristics around the model in Reynolds number range of 1.29x10⁶ to 2.14x10⁶ at various yaw angles. The wind tunnel measurements were performed to provide aerodynamic data on vehicle stability and also to build a database for validating the numerical simulation model. The CFD solver FLUENT 6.3 was used to simulate incompressible three dimensional flow with the standard k-£ turbulent models. The result of the wind tunnel tests and the numerical simulations were found to be in good agreement. The results show that the rear slant angles have significant effect on aerodynamics lateral derivatives

The Effect of Flow Characteristic on Generic Shape of an Automotive Side Mirror

In this paper, an aerodynamics effect of a simple side mirror geometry with different foot height and foot width is discussed. The numerical simulation is done by using Fluent software with two solvers which are k-epsilon standard and realizable turbulence models. The results obtained are discussed in term of velocity magnitude and pressure coefficient at side mirror surface and side window. Turbulent intensity along the horizontal air flow direction from the center of side mirror surface also has been discussed. With all these results, the best design of simple side mirror geometry has been proposed