A study of high lift aerodynamic devices on commercial aircrafts

Aerodynamic performance of aircraft wings vary with flight path conditions and depend on efficiency of high lift systems. In this work, a study on high lift devices and mechanisms that aim to increase maximum lift coefficient and reduce drag on commercial aircraft wings is discussed. Typically, such extensions are provided to main airfoil along span wise direction of wing and can increase lift coefficient by more than 100% during operation. Increasing the no of trailing edge flaps in chord wise direction could result in 100% increment in lift coefficient at a given angle of attack but leading edge slats improve lift by delaying the flow separation near stall angle of attack. Different combinations of trailing edge flaps used by Airbus, Boeing and McDonnel Douglas manufacturers are explained along with kinematic mechanisms to deploy them. The surface pressure distribution for 30P30N airfoil is evaluated using 2D vortex panel method and effects of chord wise boundary layer flow transitions on aerodynamic lift generation is discussed. The results showed better agreements with experiment data for high Reynolds number (9 million) flow conditions near stall angle of attack

Trailing Edge Bluntness Noise Characterization for Horizontal Axis Wind Turbines [HAWT] Blades

Wind turbine noise is becoming a critical issue for many offshore and land-based wind projects. In this work, we analyzed trailing edge bluntness vortex shedding noise source for a land-based turbine of size 2 MW and blade span of 38 m using original Brooks Pope and Marcolini (BPM)and modified BPM noise model. A regression-based curve fitting approach has been implemented to predict the shape function in terms of thickness to chord ratio of aerofoils used for blade. For trailing edge height of 0.1% chord, computations for sound power level were done at wind speed of 8 m/s, 17 RPM. The results showed that present approach for thickness correction predicts the noise peak of ∼78dBA at f ∼ 10 kHz which is ∼15dBA lower than that predicted from original BPM. The results were also validated using experiment data from GE 1.5sle, Siemens 2.3 MW turbines with blade lengths between 78 m and 101 m which agreed within 2% at high frequencies, f > 5 kHz. In addition, results from present approach for trailing edge bluntness noise agreed well with modified BPM by Wei et al. at high frequencies, f ∼ 10 kHz where it becomes dominant. The slope of noise curves from present approach, and modified BPM methods are lower when compared with original BPM

Concise review: aerodynamic noise prediction methods and mechanisms for wind turbines

Wind power plants are increasingly being installed across the world to combat energy deficits and climate change. One of the policy constraints for installing wind turbine plants is acoustic emissions from blades during operation. In this work, a concise review of the quasi-empirical methods important for predicting noise from rotating wind turbine blades is presented. For wind turbines, self-noise mechanisms from blades and random turbulent inflow noise sources influenced by atmospheric turbulence are two major classes which contribute to overall noise signature. It has been found that these sources exhibit narrowband and broadband frequency characteristics. Trailing edge noise from the blade is an important source at mid-band to high frequencies in overall noise spectra while at infrasonic and low frequencies, inflow and impulsive noise sources are dominant which produce high annoyance and harmful effects on inhabitants. Previous research findings related to self-noise mechanisms are discussed thoroughly to provide an insight of aerodynamically produced noise generation

Role of debt-to-equity ratio in project investment valuation, assessing risk and return in capital markets

In this paper, a case study was performed with an aim to analyze the asset returns for two different companies and the risk and returns from capital projects using standard capital asset pricing method. To demonstrate how the present values of future cash flows are influenced by discount rates when the debt-to-equity capital structure ratio is varied between 0 and 2.5 debt-to-equity. The breakeven sensitivity was also conducted in relation to different gross margin ratios of company. It was found that high value of debt-to-equity ratio yielded a flatter net present value with increase in gross margins. Capital appraisal techniques were applied to illustrate the project returns and annual cash flows and its relationship with change in cost of capital. Analysis showed that when average cost of capital is increased beyond threshold value, the net present value from the firm's project investments reduced significantly. A covariance analysis was performed to determine individual returns from two stocks traded in BSE Sensex and S&P 500 indices using the beta values. Comparing the individual and total returns of two stocks revealed that returns not only increased with increasing beta values - but also varied with earnings potential, growth rate of firm, dividend payout ratios and trading stock price. The standard deviation on portfolio of two stocks has been computed for varying asset weight ratios. It has been found that positive correlation between two stocks increased equity risk when weight ratios are not balanced in portfolio, while a negative correlation reduced equity risk