Flow distortion measurements in convoluted aero engine intakes

The unsteady flowfields generated by convoluted aero engine intakes are major sources of instabilities that can compromise the performance of the downstream turbomachinery components. Hence, there exists a need for high spatial and temporal resolution measurements that will allow a greater understanding of the aerodynamics. Stereoscopic Particle Image Velocimetry is capable of providing such fidelity but its application has been limited previously as the optical access through cylindrical ducts for air flow measurements constitutes a notable pitfall for this type of measurements. This paper presents a suite of S-PIV measurements and flow field analysis in terms of snapshot, statistical and time-averaged measurements for two S-duct configurations across a range of inlet Mach numbers. The flow assessments comprise effects of inlet Mach number and S-duct centerline offset distance. Overall, the work demonstrates the feasibility of using S-PIV techniques for determining the complex flow field at the exit of convoluted intakes with at least two orders of magnitude higher spatial resolution than the traditional pressure rake measurements allow. Analysis of the conventional distortion descriptors quantifies the dependency upon the S-duct configuration and highlights that the more aggressive duct generates twice the levels of swirl distortion than the low offset one. The analysis also shows a weak dependency of the distortion descriptor magnitude upon the inlet Mach number across the entire range of Mach numbers tested. A statistical assessment of the unsteady distortion history over the data acquisition time highlights the dominant swirl patterns of the two configurations. Such an advancement in measurement capability enables a significantly more substantial steady and unsteady flow analyses and highlights the benefits of synchronous high resolution three component velocity measurements to unlock the aerodynamics of complex engine-intake systems

Passive flow control study in a convoluted intake using Stereo Particle Image Velocimetry

The ability of vortex generators (VG) to reduce the unsteady distortion at the exit plane of an S-duct (AIP) is investigated. The 3 components of the velocity at the AIP were measured using a Stereo Particle Velocimetry system with high spatial resolution. This enabled an assessment of the synchronous swirl distortion at the duct exit. A total of nine VG cases have been investigated with a systematic variation of key design variables. Overall the VGs change the duct secondary flows and separation and are able to substantially restructure the flow field at the AIP. The pressure distortion could be reduced up to 50% and a reduction in pressure loss of 30% was achieved for the mean flow field. The VGs have a substantial influence on the unsteadiness of the flow field with a reduction in peak swirl unsteadiness of 61% and an overall reduction of unsteady swirl distortion of 67%. They also suppress the primary unsteady flow switching mechanism of the datum configuration which is associated with the oscillation of bulk and twin swirl regimes. Consequently, extreme events which leads to high swirl intensity are suppressed which lower by 45% the maximum swirl intensity for the VG cases

Dynamic flow distortion investigation in an S-duct using DDES and SPIV data

The dynamic flow distortion generated within convoluted aero-engine intakes can affect the performance and operability of the engine. There is a need for a better understanding of the main flow mechanisms which promote flow distortion at the exit of S-shaped intakes. This paper presents a detailed analysis of the main coherent structures in an S-duct flow field based on a Delayed Detached Eddy Simulation (DDES). The DDES capability to capture the characteristics of the highly unsteady flow field is demonstrated against high resolution, synchronous Stereoscopic Particle Image Velocimetry (SPIV) measurements at the Aerodynamic Interface Plane (AIP). The flow field mechanisms responsible for the main AIP perturbations are identified. Clockwise and counter-clockwise stream-wise vortices are alternately generated around the separation region at a frequency of St=0.53, which promotes the swirl switching at the AIP. Spanwise vortices are also shed from the separation region at a frequency of St=1.06, and convect downstream along the separated centreline shear layer. This results in a vertical modulation of the main loss region and a fluctuation of the velocity gradient between the high and low velocity flow at the AIP

On the Perturbation of the Three-Dimensional Stokes Flow of Micropolar Fluids by a Constant Uniform Magnetic Field in a Circular Cylinder

Modern engineering technology involves the micropolar magnetohydrodynamic flow of magnetic fluids. Here, we consider a colloidal suspension of non-conductive ferromagnetic material, which consists of small spherical particles that behave as rigid magnetic dipoles, in a carrier liquid of approximately zero conductivity and low-Reynolds number properties. The interaction of a 3D constant uniform magnetic field with the three-dimensional steady creeping motion (Stokes flow) of a viscous incompressible micropolar fluid in a circular cylinder is investigated, where the magnetization of the ferrofluid has been taken into account and the magnetic Stokes partial differential equations have been presented. Our goal is to apply the proper boundary conditions, so as to obtain the flow fields in a closed analytical form via the potential representation theory, and to study several characteristics of the flow. In view of this aim, we make use of an improved new complete and unique differential representation of magnetic Stokes flow, valid for non-axisymmetric geometries, which provides the velocity and total pressure fields in terms of easy-to-find potentials. We use these results to simulate the creeping flow of a magnetic fluid inside a circular duct and to obtain the flow fields associated with this kind of flow

Gap Domain Wall Fermions

I demonstrate that the chiral properties of Domain Wall Fermions (DWF) in the large to intermediate lattice spacing regime of QCD, 1 to 2 GeV, are significantly improved by adding to the action two standard Wilson fermions with supercritical mass equal to the negative DWF five dimensional mass. Using quenched DWF simulations I show that the eigenvalue spectrum of the transfer matrix Hamiltonian develops a substantial gap and that the residual mass decreases appreciatively. Furthermore, I confirm that topology changing remains active and that the hadron spectrum of the added Wilson fermions is above the lattice cutoff and therefore is irrelevant. I argue that this result should also hold for dynamical DWF and furthermore that it should improve the chiral properties of related fermion methods.Comment: 12 pages of text, 14 figures, added sect.6 on topology and reference

Breast Cancer Awareness Among Zayed University Female Students

Background/Aim : Breast cancer is one of the most common cancers among female population worldwide. In the United Arab Emirates, breast cancer accounts for 31-43% of all cancer types. Recently, breast cancer incidence has declined as a result of development of better diagnostic techniques. Good knowledge and awareness about early detection of signs and symptoms of the disease are the most important keys for reducing morbidity and mortality. This study aims to evaluate the level of awareness about the risk factors of breast cancer, as well as, the knowledge about screening methods among female students at Zayed University in Abu Dhabi. Method: Â A random cross-sectional survey was carried to evaluate the level of awareness about breast cancer among female students at Zayed University. A total of 100 females aged 18 “31 from different colleges were included in the study. Data were analyzed using SPSS 21 program. Chi- square test was used together with Fisher\u27s exact test, as appropriate. P value \u3c0.05 was considered significant. Results: The results show that there is a lack of knowledge and awareness about the risk factors for breast cancer. Only 12% of the participants knew that physical inactivity is a risk factor. However, 29% of the participants knew that obesity is a risk factor. Knowledge about screening methods was poor and varied according to the marital and educational status of the students. Only 17% of the total participants have done breast self-examination. Single women had less frequently performed breast self-examination compared to married women Although 40% of the participants knew about ultra sound, only 22% of the students did have the knowledge about the proper age of mammogram screening. Conclusion: The results point to the lack of awareness among female students about breast cancer, the risk factors and screening methods. Therefore, effective educational programs are required to improve the knowledge level of university students regarding breast cancer and related practices

Breast Cancer Awareness Among Zayed University Female Students

Background/Aim: Breast cancer is one of the most common cancers among female population worldwide. In the United Arab Emirates, breast cancer accounts for 31-43% of all cancer types. Recently, breast cancer incidence has declined as a result of development of better diagnostic techniques. Good knowledge and awareness about early detection of signs and symptoms of the disease are the most important keys for reducing morbidity and mortality. This study aims to evaluate the level of awareness about the risk factors of breast cancer, as well as, the knowledge about screening methods among female students at Zayed University in Abu Dhabi. Method:  A random cross-sectional survey was carried to evaluate the level of awareness about breast cancer among female students at Zayed University. A total of 100 females aged 18–31 from different colleges were included in the study. Data were analyzed using SPSS 21 program. Chi- square test was used together with Fisher’s exact test, as appropriate. P value <0.05 was considered significant. Results: The results show that there is a lack of knowledge and awareness about the risk factors for breast cancer. Only 12% of the participants knew that physical inactivity is a risk factor. However, 29% of the participants knew that obesity is a risk factor. Knowledge about screening methods was poor and varied according to the marital and educational status of the students. Only 17% of the total participants have done breast self-examination. Single women had less frequently performed breast self-examination compared to married women Although 40% of the participants knew about ultra sound, only 22% of the students did have the knowledge about the proper age of mammogram screening. Conclusion: The results point to the lack of awareness among female students about breast cancer, the risk factors and screening methods. Therefore, effective educational programs are required to improve the knowledge level of university students regarding breast cancer and related practices

Pressure flowfield and inlet flow distortion metrics reconstruction from velocity data

Complex engine intakes are susceptible to unsteady flow distortions that may compromise the propulsion system operability. Hence, the need for high spatial and temporal resolution flow information is essential to aid the development of distortion tolerant, closely coupled propulsion systems. Stereoscopic PIV methods have been successfully applied to these flows offering synchronous velocity datasets of high spatial resolution across the Aerodynamic Interface Plane. However, total pressure distortion measurements are still typically provided by low bandwidth, intrusive total pressure rakes of low spatial resolution which results in limited characterisation of the total pressure distortion. This limitation can potentially be addressed by pressure field reconstruction from non-intrusive, high resolution velocity data. A range of reconstruction methods are assessed based on representative data from steady and unsteady computational simulations of an S-duct configuration. In addition to the reconstructed total pressure field, the impact on the key distortion metrics is assessed. The effect of Mach number is considered. Overall the reconstruction methods show that the distortion metrics can be determined with sufficient accuracy to indicate that there is a potential benefit from exploiting high resolution velocity measurements in evaluating total pressure distortion

The impact of heat exchanger degradation on the performance of a humid air turbine system for power generation

This paper aims to analyse the impact of air-water heat exchanger’s degradation on the performance of a reheated humid air turbine system for power generation applications. A number of thermal models to simulate the performance of the various sub-systems was put together and validated against experimental data. The performance degradation of the heat exchangers is characterised by means of a degradation coefficient, which is used to drive the cycle into off-design and part-load conditions when degradation is accounted for. Three heat exchanger design scenarioswere investigated, namely a low, a medium and a high effectiveness in order for the impact of the degradation penalties on cycle thermal efficiency to be determined. The performance deterioration of the heat exchangers is also analysed from an exergetic point of view in order to identify the key sources that penalise the thermal efficiency of the humid air turbine system. The degradation analysis shows that typical levels of intercooler deterioration cause notable penalties in the cycle performance, reducing its thermal efficiency and power output by 1.8 percentage points and 28% respectively compared to the un-degraded operation. The exergy analysis showed that the deterioration of the intercooler also penalises the efficiency of the low pressure compressor and reheater, which contribute to the performance penalty of the cycle too. It is also found that the degradation of the intercooler can also lead to operability penalties at the low pressure compressor by reducing its surge margin. The effects of the deterioration of the aftercooler and economiser were found to only have a weak effect on the system’s performance. The outcome of the work constitutes a step forward in understanding of the performance behaviour of an advanced cycle when heat exchanger degradation is present