CFD simulation of flow past MAV wings

Turbulent flow past low aspect ratio (AR) thin wing used for two different MAV (Micro Air Vehicles) configurations viz. Black Kite and Golden Hawk has been carried out in order to analyze their aerodynamic characteristics. The Reynolds (Re) number for these two wings based on the root chord are 2.4´105 and 1.72´ 105 respectively. These simulations have been carried out using the in-house flow solution code to solve the Unsteady Reynolds Averaged Navier Stokes (URANS) equations coupled to different turbulence models. The standard k-e model has been used to simulate the turbulence for the Black Kite wing. The influence of three different turbulence models (standard k-e, SA and SST) in predicting the aerodynamic coefficient has been studied for the Golden Hawk configuration. In the present study the aerodynamic characteristics computed for the two wing configurations are compared with the CSIR-NAL experiments. The cross flow patterns and the tip vortex for the Golden Hawk wing are presented and discussed

Fluid structure interaction of a two-dimensional membrane in a flow with a pressure gradient with application to convertible car roofs

Original article can be found at : http://www.sciencedirect.com/ Copyright ElsevierThe flow-induced deformation of a membrane in a flow with a pressure gradient is studied. The investigation focuses on the deformation of aerodynamically loaded convertible car roofs. A computational methodology is developed with a line-element structural model that incorporates initial slackness of the flexible roof material. The computed flow–structure interaction yields stable solutions, the flexible roof settling into static equilibrium. The interaction converges to a static deformation within 1% difference in the displacement variable after three iterations between fluid and structural codes. Reasonably accurate predictions, to within 7%, are possible using only a single iteration between the fluid and the structural codes for the model problem studied herein. However, the deformation results are shown to be highly dependent on the physical parameters that are used in the calculation. Accurate representation of initial geometry, material properties and slackness should be found before the predictive benefits of the fluid–structure computations are sought. The iterative methodology overcomplicates the computation of deformation for the relatively small displacements encountered for the model problem studied herein. Such an approach would be better suited to applications with large amplitude displacements such as those encountered in sail design or deployment of a parachute.Peer reviewedFinal Accepted Versio

Assessing causes of contractual disputes from different type of condition of contracts

In a construction industry, a Condition of Contract (CoC) is primarily used to ensure a project can be delivered successfully with minimum disputes. The contractual disputes rooted from many factors, including from the improper management of conflict between parties in the project, misinterpretation of the CoC, lack of documentation, and discrepancies and ambiguities of documents which may lead to as cost overruns, project delay and project cashflow. Thus, a comprehensive CoC plays a significant role to express the rights and obligations of the main contracting parties. CoC functions in stating to each party on what they shall do and to the extent of their entitlement of rights and obligations under the contract. Despite having various of published CoC such as PAM Contract and series of PWD Form of Contract to govern the construction projects, numerous construction cases in relation to contractual disputes are still increasing over the years and there has been little discussion about the causes of disputes. It indicates the ineffectiveness of the contract provision in the CoC. Hence, this study presents thorough review of the disputes occurs in the construction industry by outlining the issues raised in the court cases. This scenario has paved this paper to achieve the objectives of the research, including to identify the factors attribute to the construction dispute and to investigate the provision in CoC that caused the contractual disputes. The data collection used was mainly through literature synthesis and surveys. The results revealed that there are five attributes of construction disputes. The findings of the paper would be beneficial to practitioners in increasing their awareness of the flaws in the CoC and could be helpful in mitigating the disputes

Design and development of an automated metered dose inhaler (MDI) for asthmatic patient

To date, infant with illness associated with the pulmonary airway is treated by a doctor using a spacer device with metered dose inhaler (MDI) to allow the infant to breathe in the medication known as salbutamol. Current asthma spacer does not provide systematic way of monitoring and displaying the percentage value of the propellant. Furthermore, user non-compliance is found to contribute towards longer recovery rate. Therefore, this product is designed and developed capable of detecting the propellant level inhaled by the infant by using a MQ-6 gas sensor and monitoring its percentage value. The display of available puffs of MDI canister and the battery indicator for the system are also included in the device. The automated actuation MDI was required a push button to press the MDI canister where this project utilised Arduino Nano as the microcontroller to control the system operation and all the reading values will be displayed on the OLED. RGB LED is also used to visualise the propellant level. The obtained results of the detection of propellant in voltage from the MQ-6 gas sensors were analysed in MATLAB to make comparison through the obtained results. Without propellant, voltage recorded is 0.640±0.024V whereas high concentration of propellant displayed voltage of 1.126±0.020V. The mean standard error rate of propellant detection is 5.584%. The first design of the actuation device and interface monitoring display of automated MDI were recorded the highest percentage which is 75% and 80%. The concentration of propellant depends on the ambient temperature due to the MQ-6 gas sensor required minimum working temperature between 20oC to 22oC. The mean weight of the MDI canister for each puff is 6.257mg and the standard deviation is 3.629mg. Due to experiment conducted, the speed and pressure of pressing MDI canister causes variability in the released of salbutamol and propellant. Observation proved that ambient temperature and propellant released amount also influenced the final reading from the automated actuation MDI

Numerical analysis and simulation of an assured crew return vehicle flow field

A lifting body was proposed as a candidate for the Assured Crew Return Vehicle (ACRV) which will serve as a crew rescue vehicle for the Space Station Freedom. The focus is on body surface definition, both surface and volume grid definition, and the computation of inviscid flow fields about the vehicle at wind tunnel conditions. Very good agreement is shown between the computed aerodynamic characteristics of the vehicle at M(sub infinity) = 10 and those measured in wind tunnel tests at high Reynolds numbers

Development of a computer code for calculating the steady super/hypersonic inviscid flow around real configurations. Volume 1: Computational technique

A numerical procedure has been developed to compute the inviscid super/hypersonic flow field about complex vehicle geometries accurately and efficiently. A second order accurate finite difference scheme is used to integrate the three dimensional Euler equations in regions of continuous flow, while all shock waves are computed as discontinuities via the Rankine Hugoniot jump conditions. Conformal mappings are used to develop a computational grid. The effects of blunt nose entropy layers are computed in detail. Real gas effects for equilibrium air are included using curve fits of Mollier charts. Typical calculated results for shuttle orbiter, hypersonic transport, and supersonic aircraft configurations are included to demonstrate the usefulness of this tool

Development of a non-linear simulation for generic hypersonic vehicles - ASUHS1

A nonlinear simulation is developed to model the longitudinal motion of a vehicle in hypersonic flight. The equations of motion pertinent to this study are presented. Analytic expressions for the aerodynamic forces acting on a hypersonic vehicle which were obtained from Newtonian Impact Theory are further developed. The control surface forces are further examined to incorporate vehicle elastic motion. The purpose is to establish feasible equations of motion which combine rigid body, elastic, and aeropropulsive dynamics for use in nonlinear simulations. The software package SIMULINK is used to implement the simulation. Also discussed are issues needing additional attention and potential problems associated with the implementation (with proposed solutions)

A direct method for calculation of the flow about an axisymmetric blunt body at angle of attack

Direct calculation method for supersonic inviscid flow around axisymmetric blunt body with conically reentrant afterbody flying at large angle of attac

Simultaneous Optimal Uncertainty Apportionment and Robust Design Optimization of Systems Governed by Ordinary Differential Equations

The inclusion of uncertainty in design is of paramount practical importance because all real-life systems are affected by it. Designs that ignore uncertainty often lead to poor robustness, suboptimal performance, and higher build costs. Treatment of small geometric uncertainty in the context of manufacturing tolerances is a well studied topic. Traditional sequential design methodologies have recently been replaced by concurrent optimal design methodologies where optimal system parameters are simultaneously determined along with optimally allocated tolerances; this allows to reduce manufacturing costs while increasing performance. However, the state of the art approaches remain limited in that they can only treat geometric related uncertainties restricted to be small in magnitude. This work proposes a novel framework to perform robust design optimization concurrently with optimal uncertainty apportionment for dynamical systems governed by ordinary differential equations. The proposed framework considerably expands the capabilities of contemporary methods by enabling the treatment of both geometric and non-geometric uncertainties in a unified manner. Additionally, uncertainties are allowed to be large in magnitude and the governing constitutive relations may be highly nonlinear. In the proposed framework, uncertainties are modeled using Generalized Polynomial Chaos and are solved quantitatively using a least-square collocation method. The computational efficiency of this approach allows statistical moments of the uncertain system to be explicitly included in the optimization-based design process. The framework formulates design problems as constrained multi-objective optimization problems, thus enabling the characterization of a Pareto optimal trade-off curve that is off-set from the traditional deterministic optimal trade-off curve. The Pareto off-set is shown to be a result of the additional statistical moment information formulated in the objective and constraint relations that account for the system uncertainties. Therefore, the Pareto trade-off curve from the new framework characterizes the entire family of systems within the probability space; consequently, designers are able to produce robust and optimally performing systems at an optimal manufacturing cost. A kinematic tolerance analysis case-study is presented first to illustrate how the proposed methodology can be applied to treat geometric tolerances. A nonlinear vehicle suspension design problem, subject to parametric uncertainty, illustrates the capability of the new framework to produce an optimal design at an optimal manufacturing cost, accounting for the entire family of systems within the associated probability space. This case-study highlights the general nature of the new framework which is capable of optimally allocating uncertainties of multiple types and with large magnitudes in a single calculation