Modeling of viscous flows in two-dimensional turbomachinery cascade via viscous-inviscid interaction method

[Abstract]: A two-dimensional time-accurate time-marching viscous flow solver employing the viscous-inviscid interaction method suitable for turbomachinery applications is described. The inviscid main flow solver uses the second-order accurate cellvertex finite-volume spatial discretisation and fourth-order accurate Runge-Kutta temporal integration. The viscous effect due to boundary layer development on the blade surfaces and wakes are modelled using an independent one-dimensional boundary layer subroutine capable of modelling laminar, transition and fully turbulent flows. The solver has been applied to subsonic, transonic and supersonic flow in a cascade of nozzle blades. The results are compared with the experimental data and they showed very good agreemen

A holey fiber based Brillouin laser

We demonstrate for the first time a Brillouin laser based on a Holey Fiber (HF). Using a simple Fabry-Perot resonator scheme containing a 75m long highly nonlinear HF with an effective area of 2.85µm2 we obtain a threshold of 125mW and a slope efficiency of ~70%

Simulation of sub-drains performance using visual MODFLOW for slope water seepage Problem

Numerical simulation technique was used for investigating water seepage problem at the Botanic Park Kuala Lumpur. A proposed sub-drains installation in problematic site location was simulated using Modular Three-Dimensional Finite Difference Groundwater Flow (MODFLOW) software. The results of simulation heads during transient condition showed that heads in between 43 m (water seepage occurred at level 2) until 45 m (water seepage occurred at level 4) which heads measurement are referred to mean sea level. However, elevations measurements for level 2 showed the values between 41 to 42 m from mean sea level and elevations for level 4 between 42 to 45 m from mean sea level. These results indicated an increase in heads for level 2 and level 4 between 1 to 2 m when compared to elevations slope at the level 2 and level 4. The head increases surpass the elevation level of the slope area that causing water seepage at level 2 and level 4. In order to overcome this problems, the heads level need to be decrease to 1 until 2 m by using two options of sub-drain dimension size. Sub-drain with the dimension of 0.0750 m (diameter), 0.10 m (length) and using 4.90 m spacing was the best method to use as it was able to decrease the heads to the required levels of 1 to 2 m

Simulation of sub-drains performance using visual MODFLOW for slope water seepage Problem

Numerical simulation technique was used for investigating water seepage problem at the Botanic Park Kuala Lumpur. A proposed sub-drains installation in problematic site location was simulated using Modular Three-Dimensional Finite Difference Groundwater Flow (MODFLOW) software. The results of simulation heads during transient condition showed that heads in between 43 m (water seepage occurred at level 2) until 45 m (water seepage occurred at level 4) which heads measurement are referred to mean sea level. However, elevations measurements for level 2 showed the values between 41 to 42 m from mean sea level and elevations for level 4 between 42 to 45 m from mean sea level. These results indicated an increase in heads for level 2 and level 4 between 1 to 2 m when compared to elevations slope at the level 2 and level 4. The head increases surpass the elevation level of the slope area that causing water seepage at level 2 and level 4. In order to overcome this problems, the heads level need to be decrease to 1 until 2 m by using two options of sub-drain dimension size. Sub-drain with the dimension of 0.0750 m (diameter), 0.10 m (length) and using 4.90 m spacing was the best method to use as it was able to decrease the heads to the required levels of 1 to 2 m

Impact of Teaching Cohesive Devices on L2 Students\u27 Language Accuracy in Written Production

A well-written text is not only grammatical, but also cohesive and coherent. Cohesive devices play the most basic role in cohesion of a text and should be taken into consideration in teaching writing. This paper reports on a study investigating the impact of teaching academic text cohesive devices on L2 students\u27 language accuracy in written production. The main objective of the study is to find out if teaching cohesive devices would enhance students\u27 prior knowledge and subsequently result in increased written language accuracy. Based on a pre-post-test research design, 40 students enrolled in English for Academic Purposes course at a university in Malaysia were engaged as participants. A note-taking test was conducted prior to and post intervention. The intervention consisted of lessons on academic text cohesive devices. The data was then analysed and reported using descriptive statistics and paired sample t-test. From the findings, it is clear that there is an increase in the minimum and maximum scores as well as in the mean scores between the pre- and post-test. More importantly, there is evidently a significant improvement in the participants\u27 post-test language accuracy as evaluated through number of error-free t-units. In sum, the teaching of academic text cohesive devices does have a significant impact on language accuracy in written production. Hence, this study recommends L2 learners\u27 prior knowledge activation to enhance written language accuracy

Development of a Short Duration Hyprsonic Test Facility at Universiti Tenaga Nasional

This paper describes the development of a short duration hypersonic test facility at the College of Engineering, Universiti Tenaga Nasional (UNITEN). The facility is the first of its kind in Malaysia. The facility will allow various researches to be done in the field of high speed supersonic and hypersonic flows. It is designed so that it can be used as a free piston tunnel, shock tube and shock tunnel. The maximum mach number obtainable depends on the type of the driver and driven gases. It is shown that a mach number of 4 can be achieved if CO2 is used as the driven gas and Helium is used as the driver gas with diaphragm pressure ratio of 74.76. Experimental measurements were performed with the facility working as shock tube. The barrel temperature was measured using in-house developed fast response surface junction E-type thermocouple while the pressure was measured using fast response quartz pressure transducer. The pressure and temperature results clearly show the formation of shock wave and its reflection causing the pressure and temperature to increase rapidly

Error correction and uncertainty measurement of short-open-load calibration standards on a new concept of software defined instrumentation for microwave network analysis

Software-Defined Radio (SDR) has appeared as a sufficient framework for the development and testing of the measurement systems such as a signal generator, signal analyzer, and network analysis used in the network analyzer. However, most of researchers or scientists still rely on commercial analyzers were larger benchtop instruments, highly cost investment and minimum software intervention. In this paper, a new concepts measurement revolution called as Software Defined Instrumentation (SDI) on network analysis is presented, which is based on reconfigurable SDR, a low-cost implementation, ability to access RF chain and utilizing open source signal processing framework. As a result, a Vector Network Analyzer (VNA) has been successful implemented by deploying an SDR platform, test sets, and data acquisition from the GNU Radio software in host PC. The known calibration process on SHORT-OPEN-LOAD (SOL) technique is validated to ensure measurement data from this SDI free from systematic error. Two types of SOL calibration standards used for a comparison study to validate the SDI measurement system which is capable of generating the response on the differential of standard quality and accuracy of standards kits. Finally, calibration uncertainty analysis is also presented in this work by utilizing RF open source package without any cost addition

Area contraction effect on shock tube performance, numerical and experimental study

The paper presents numerical and experimental study on the effect of area contraction in shock tube facility. The shock tube is the main component of short duration test facility at The Universiti Tenaga Nasional (UNITEN), Malaysia. In the shock tube, a small area contraction in form of a removable bush was facilitated adjacent to the diaphragm section. The flow process was simulated using a two-dimensional time-accurate Navier-Stokes solver. The solver uses second order accurate cell-vertex finite volume spatial discretization and fourth orders accurate Runge-Kutta temporal integration. In this study, the solver was programmed based on the dimensions and configuration of UNITEN’s shock tube facility. The numerical results were validated with experimental data from the ground based test facility. Numerical pressure histories were found to be in accordance with the experimental data. For further investigations, simulations were conducted for different operating conditions. The results showed that shock tube performance in term of producing shock wave and steady gas flow is highly influenced by area contraction in the diaphragm section. The shock wave strength and speed decreased by 18% and 8% respectively

Is Halal Certification Process “Green”?

These days, the environmental perspective on operations is becoming more common. In fact, any effort in improving efficiency in the organization is closely related to sustainability of our environment. The Environmental Management System (EMS) certification such as ISO 14001 has been accepted as the world standard. In addition to these ISO standards, there are other certifications such as Halal certification. There is no research that investigates the relationship between Halal Certification process and its effect on our environment. Hence, our main research question is that is Halal Certification process can be considered as environmental friendly? In this paper, we argue that Halal Certification also contributes towards green initiatives. We used EDC-UUM as our case study. EDC-UUM is actively seeking the Halal certification from Malaysian authority agency or JAKIM. In this study, we assessed the perception of the EDC-UUM staff on the issue of going green. The findings and implications are discussed in the paper

The Effects of Area Contraction on Shock Wave Strength and Peak Pressure in Shock Tube

This paper presents an experimental investigation into the effects of area contraction on shock wave strength and peak pressure in a shock tube. The shock tube is an important component of the short duration, high speed fluid flow test facility, available at the Universiti Tenaga Nasional (UNITEN), Malaysia. The area contraction was facilitated by positioning a bush adjacent to the primary diaphragm section, which separates the driver and driven sections. Experimental measurements were performed with and without the presence of the bush, at various diaphragm pressure ratios, which is the ratio of air pressure between the driver (high pressure) and driven (low pressure) sections. The instantaneous static pressure variations were measured at two locations close to the driven tube end wall, using high sensitivity pressure sensors, which allow the shock wave strength, shock wave speed and peak pressure to be analysed. The results reveal that the area contraction significantly reduces the shock wave strength, shock wave speed and peak pressure. At a diaphragm pressure ratio of 10, the shock wave strength decreases by 18%, the peak pressure decreases by 30% and the shock wave speed decreases by 8%