Climate change creativity for cirrus clouds and contrails control

Cirrus ice clouds formed normally in the upper troposphere and contrails, shed by aircraft, impact climate and global warming due to prevailing cirrus clouds ice water content and crystal size. Contrail cirrus impact on climate change also comprises their influence on water vapor in the higher troposphere layer, which alter the infrared heat emission. The effect of commercial flights to climate change is of serious concern to the environmental conservation and climate change mitigation efforts. Therefore, it is imperative that the physical characteristics of cirrus clouds, contrails and their interactions be understood to devise anthropogenic solutions

Progress and development of Coanda jet and vortex cell for aerodynamic surface circulation control - an overview

Coandă jet has always been referred to in the consideration of various flow control methods to enhance aerodynamic performance, i.e. to enhance lift, reduce drag and delay stall at higher angle of attack, along with continuous, synthetic and pulsed jets, compliant surface, vortex-cell, and the like. Coandă jet has also been applied in the development of novel aircrafts for short take off, while another circulation enhancement technique known as Trapped Vortex Cavity (TVC) is currently being given significant considerations. It is with such motivation that within the aerodynamics surface blowing techniques, Coandă jet and vortex-cell will be reviewed, to assess their characteristics in dramatically alter the behavior of aerodynamic components such as airfoils, wings, and bodies. Capitalizing on a host of research and technology development efforts on Coandă and surface blowing circulation enhancement, the present work reviews the influence, effectiveness and configuration of airfoil surface blowing of Coandă-jet and Trapped Vortex Cavity in circulation enhancement and control of aerodynamic surfaces. The crux of the TVC active research is their stabilization, while Coandă enhanced lift enhancement technique has, to a certain extent reached a stage that it can be easily implemented with advantage

Simple Method to Calculate the Oscillating Lift on a Circular Cylinder in Potential Flow

Abstract. A simple potential flow model is presented to calculate the oscillating lift on a circular cylinder. In essence, the time dependent lift acting on a cylinder is due to the presence of a vortex shed off the separation point on the cylinder. The vortex strength and its trajectory is predicted employing the condition of zero force on the vortex and its feeding vortex sheet. The vortex breaks away from the cylinder and is convected by the fluid after the vortex strength reaches a maximum value, and another vortex is shed at the other side of the cylinder. Oscillating lift with the right order of magnitude of available experimental results was predicted. For subcritical flow, good agreement is obtained between the predicted Strouhal number and that found experimentally.  Ringkasan. Suatu model aliran potensial sederhana diuraikan untuk menghitung gaya angkat yang berosilasi pada silinder lingkaran. Pada dasarnya, gaya angkat yang berosilasi ini disebabkan karena adanya vortex yang dilepaskan oleh silinder dari titik pemisahan. Kekuatan vortex dan lintasannya dihitung dengan menggunakan syarat bahwa gaya pada vortex dan bidang vortex yang menumbuhkannya harus sama dengan nol. Vortex ini terputus dari silinder pada waktu kekuatannya mencapai maksimum, dan vortex yang lain mulai dilepaskan pada sisi silinder yang lain. Hasil perhitungan menunjukkan harga gaya angkat maksimum yang mendekati harga yang diperoleh secara eksperimentil. Demikian pula, untuk aliran subkritis, diperoleh hasil perhitungan bilangan Strouhal yang mendekati harga yang diperoleh secara eksperimen

Unified aerodynamic-acoustic formulation for aero-acoustic structure coupling

Conventional coupled BE/FE (Boundary-Element/Finite-Element) method and modeling of structural-acoustic interaction has shown its promise and potential in the design and analysis of various structural-acoustic interaction applications. Unified combined acoustic and aerodynamic loading on the structure is synthesized using two approaches. Firstly, by linear superposition of the acoustic pressure disturbance to the aeroelastic problem, the effect of acoustic pressure disturbance to the aeroelastic structure is considered to consist of structural motion independent incident acoustic pressure and structural motion dependent acoustic pressure, which is known as the scattering pressure, referred here as the acoustic aerodynamic analogy. Secondly, by synthesizing the acoustic and aerodynamic effects on elastic structure using an elegant, effective and unified approach, both acoustic and aerodynamic effect on solid structural boundaries can be formulated as a boundary value problem governed by second order differential equations which lead to solutions expressible as surface integral equations. The unified formulation of the acousto-aeroelastic problem is amenable for simultaneous solution, although certain prevailing situations allow the solution of the equations independently. For this purpose, the unsteady aerodynamic problem which was earlier utilizes well-established lifting surface method is reformulated using Boundary Element (BE) approach. These schemes are outlined and worked out with examples

Vinti's Surface Density as a Means of Representing the Earth's Disturbance Potential

Abstract. Vinti's method of representing the potential of the earth in two parts, with the first part represented by spheroidal potential and the second part being the earth disturbance potential, is outlined. The earth's disturbance potential is then represented as a surface distribution σ of mass density of variable sign over a sphere S just clearing the earth. The feasibility of the method is evaluated by calculating the distribution of o from satellite determination of the harmonic coefficients. Ringkasan. Suatu metoda untuk menyatakan potensial bumi berdasarkan teori Vinti diuraikan. Menurut metoda ini, potensial bumi dinyatakan sebagai jumlah potensial utama, yang diperoleh sebagai potensial spheroid, dan potensial gangguan, yang dinyatakan sebagai distribusi kerapatan masa permukaan pada suatu bola yang tepat menyelubungi bumi. Kegunaan metoda ini diuji dengan menghitung distribusi σ dengan menggunakan koefisien-koefisien harmonik yang ditentukan dari analisa data satelit

Computational simulation for analysis and synthesis of impact resilient structure

Impact resilient structures are of great interest in many engineering applications varying from civil, land vehicle, aircraft and space structures, to mention a few examples. To design such structure, one has to resort fundamental principles and take into account progress in analytical and computational approaches as well as in material science and technology. With such perspectives, this work looks at a generic beam and plate structure subject to impact loading and carry out analysis and numerical simulation. The first objective of the work is to develop a computational algorithm to analyze flat plate as a generic structure subjected to impact loading for numerical simulation and parametric study. The analysis will be based on dynamic response analysis. Consideration is given to the elastic-plastic region. The second objective is to utilize the computational algorithm for direct numerical simulation, and as a parallel scheme, commercial off-the shelf numerical code is utilized for parametric study, optimization and synthesis. Through such analysis and numerical simulation, effort is devoted to arrive at an optimum configuration in terms of loading, structural dimensions, material properties and composite lay-up, among others. Results will be discussed in view of practical applications

Overview of Coandă MAV as an Aerial Robotic Platform

With the increasing need of micro‐air‐vehicles (MAVs) and advances in MAV technology, Coandă MAVs offer new promises and challenges. In this context, Coandă MAVs capabilities are analyzed. As a baseline, a mathematical model for a spherical Coandă MAV in hover and translatory motion is developed and analyzed from first physical principles. A computational fluid dynamic (CFD) simulations for a Coandă MAV generic model are carried out to assess the theoretical prediction and obtaining further physical insight on the Coandă MAV flow physics. The mathematical model and performance measures are developed to assess the capability of the semi‐spherical Coandă MAV in performing effective flight as an aerial robotic platform, as indicated by the relationships between the relevant parameters of the mathematical model of the Coandă MAV to its system of flight forces

Locally Linearized Solution of Lifting Transonic Flow by Method of Parametric Differentiation

The governing equation of transonic small disturbance flow present a non-linear partial differential equation which is difficult to solve. The method of parametric differentiation reduces the non-linear partial differential equation of transonic flow into an ordinary differential equation with variable coefficient, which is generally much simple to solve. Further simplification is introduced, as also done in the method of local linearization, by assuming (1-M12) to vary sufficiently slowly, so that in some part of the analysis its derivatives with respect to x can be disregarded. Based upon these methods, the lifting transonic flow was analyzed. For the subsonic and supersonic parts, closed form solutions were obtained. For the case M1 â‰ˆ 1, the method yields an integral equation, which can be solved by an iterative scheme starting from the non-lifting solution.

Proof of concept MFD optimization of the aftbody geometry of axisymmetric slender body based on wave drag considerations

A comprehensive, universally valid, elegant and yet simple method to design slender axisymmetric body of minimum wave drag in transonic and supersonic flows is developed. Computational aerodynamics is also used as a tool for numerical experiments in gaining physical understanding of the drag mechanism due to the geometry of the aftbody, such as the correlation between wave drag and wave distribution of the aftbody geometry. The method utilizes MFD (modified feasible direction) based optimization program, along with the linear slender body aerodynamics, for its elegance and generic optimization convenience. The efforts are focused on inviscid flow. A practical method of reducing the wave drag of a given body is developed for both bodies with pointed end and with base area, using shock wave generator at a particular location on the aftbody. The results show that the MFD optimization program can be effectively utilized in an aerodynamic optimization problem