Studi Numerik Perbandingan Kinerja dan Medan Aliran Turbin Vortex Gravitasi dengan Tipe Sudu Lengkung Backward dan Forward

<p><em>The interaction of turbine blades with vortex flow in micro-hydro power plants based on gravity vortex is still not clearly clarified, therefore numerical simulation is a tool to produce flow visualization that helps analyze the performance of experimental results. This study aims to compare the performance of a gravity vortex flow power generator using a conical basin with a </em><em>inclined</em><em> backward and </em><em>inclined </em><em>forward blade design using a numerical simulation approach. The simulation begins by validating the results of torque performance and visualizing the flow of experimental research conducted by previous researchers, then the simulation settings are used to compare the performance of the </em><em>inclined</em><em> backward and </em><em>inclined </em><em>forward blade turbine designs with variations in turbine rotation speed of 80, 120, 160 and 180 rpm. The simulation results show that the curved backward blade performance is better than the forward curved blade which is supported by visualizing the free surface flow and static pressure contours on the blade surface.</em><em></em></p>

Media Entertainment, Flow Experiences, and the Synchronization of Audiences

Media entertainment frequently elicits rapt attention, loss of self-consciousness, high levels of enjoyment along with a sense that time is passing more quickly or more slowly than usual. This state is often referred to as flow. For over two decades, scholars have sought to understand when and why media produce flow experiences in audiences. The synchronization theory of flow (STF) advanced flow research by specifying the neural underpinnings of flow experiences and how these neural substrates are influenced by entertaining media. In the intervening years, research from a variety of fields has provided support for the core predictions of STF and has highlighted promising areas for future investigation. This chapter reviews the current state and future directions of STF, focusing on its potential for creating a bridge between media entertainment research and other vibrant research domains including motivated decision-making and neuroaesthetics.

Numerical Simulations of Combustion Instabilities in a Combustor with an Augmentor-Like Geometry

With the goal of assessing the capability of Computational Fluid Dynamics (CFD) to simulate combustion instabilities, the present work considers a premixed, bluff-body-stabilized combustor with well-defined inlet and outlet boundary conditions. The present simulations produce flow behaviors in good qualitative agreement with experimental observations. Notably, the flame flapping and standing acoustic waves seen in the experiments are reproduced by the simulations. Moreover, present predictions for the dominant instability frequency have an error of 7% and those of the rmspressure fluctuations show an error of 16%. In addition, an analysis of simulation results for the limit cycle complements previous experimental analyses by supporting the presence of an active frequency-locking mechanism.

HIGHLY-RESOLVED NUMERICAL AND LABORATORY ANALYSIS FOR NONBREAKING SOLITARY WAVE SWASH OVER A STEEP SLOPE

In this paper we study the swash processes generated by a nonbreaking solitary wave running up and down a steep slope (1:3). We use experimental data to study flow features and velocities inside the boundary layer, and numerical modelling to investigate variables not measured during the laboratory experiments, such as pressures and bottom shear stress. We focus on the mechanisms that produce flow separation and vortex formation. Particularly, we study a system of vortices generated under a hydraulic jump during the rundown phase, which was first observed by Matsunaga & Honji (1980).

Microstructure Evolution in a 6082 Aluminium Alloy during Thermomechanical Treatment

Thermomechanical treatments of age-hardenable wrought aluminium alloys provoke microstructural changes that involve the movement, arrangement, and annihilation of dislocations, the movement of boundaries, and the formation or dissolution of phases. Cold and hot compression tests are carried out using a Gleeble® 3800 machine to produce flow data as well as deformed samples for metallography. Electron backscattered diffraction and light optical microscopy were used to characterise the microstructure after plastic deformation and heat treatments. Models based on dislocation densities are developed to describe strain hardening, dynamic recovery, and static recrystallisation. The models can describe both the flow and the microstructure evolutions at deformations from room temperatures to 450 °C. The static recrystallisation and static recovery phenomena are modelled as a continuation of the deformation model. The recrystallisation model accounts also for the effect of the intermetallic particles in the movements of boundaries.

Using Eye Tracking to Evaluate the Usability of Flow Maps

Flow maps allow users to perceive not only the location where interactions take place, but also the direction and volume of events. Previous studies have proposed numerous methods to produce flow maps. However, how to evaluate the usability of flow maps has not been well documented. In this study, we combined eye-tracking and questionnaire methods to evaluate the usability of flow maps through comparisons between (a) straight lines and curves and (b) line thicknesses and color gradients. The results show that curved flows are more effective than straight flows. Maps with curved flows have more correct answers, fixations, and percentages of fixations in areas of interest. Furthermore, we find that the curved flows require longer finish times but exhibit smaller times to first fixation than straight flows. In addition, we find that using color gradients to indicate the flow volume is significantly more effective than the application of different line thicknesses, which is mainly reflected by the presence of more correct answers in the color-gradient group. These empirical studies could help improve the usability of flow maps employed to visualize geo-data.

The Behavior of the Casing Boundary Layer With the Presence of Tip Leakage Vortex

Casing boundary layer effectively places a limit on the pressure rise capability achievable by the compressor. The separation of the casing boundary layer not only produce flow loss but also closely related to the compressor rotating stall. The motivation of this paper is to present a viewpoint that the casing boundary layer should be paid attention to in parallel with other flow factors on rotating stall trigger. This paper illustrates the casing boundary layer behavior by displaying its separation phenomena with the presence of tip leakage vortex at different flow conditions. Skin friction lines and the corresponding absolute streamlines are used to demonstrate the three-dimensional flow patterns on and near the casing. The results depict a Saddle, a Node and several tufts of skin friction lines dividing the passage into four zones. The tip leakage vortex is enfolded within one of the zones by the separated flows. All the flows in each blade passage are confined within the passage as long as the compressor is stable. The casing boundary layer of a transonic compressor is also examined in the same way, which results in qualitatively similar zonal flows that enfolds the tip leakage vortex. This research develops a new way to study the casing boundary layer in rotating compressors. The results may provide a first-principle based explanation to stalling mechanisms for compressors that are casing sensitive.

Rayleigh Wave Theory

In this chapter, the mechanism for generating fluctuating reservoir pressures will be explored. The generation of surface waves and fluctuating pressures in the upstream reservoir due to gate motion will be examined. The energy input into surface waves is dissipated, or dispersed, as the waves travel away from the structure. These waves are called dispersive waves. In this chapter, the mathematical description of these dispersive waves will be developed. Streamwise vibration will always produce a periodic fluctuation of the reservoir depth, thereby inducing dispersive water waves on the free surface. In addition, both the streamwise bending vibrations and the vertical vibrations of the gate can potentially produce flow rate variation beneath the gate resulting in fluctuating reservoir depth, and inducing dispersive waves on the free surface. The theoretical framework for coupling discharge fluctuations and dispersive waves with gate vibration to supply energy to the gate motion will be developed.

Time-Varying Load Analysis on the Rotor-Bearing System for Twin-Screw Compressors

Shaft and rotor deformation caused by the high pressure load, temperature and other external forces in the twin-screw compressor may produce flow leakage, tooth wear and bearing failure. A time-varying load analysis procedure is proposed in this paper to obtain the gas torques on rotors, bearing forces and the shaft deflections for the twin-screw compressor. Further, the calculated forces are compared with the existed well-known software to verify the correctness of the proposed method. Also, the forces on each bearings and the shaft deflection are predicted through KISSsoft modeling technique in this paper.

Processing of Underway CTD Data

A processing methodology for computation of accurate salinity from measurements with an underway CTD (UCTD) is presented. The UCTD is a rapidly profiling sensor package lacking a pump that relies on instrument motion to produce flow through the conductivity cell. With variable instrument descent rate, the flow through the cell is not constant, and this has important implications for the processing. As expected, the misalignment of the raw temperature and conductivity is found to be a function of the instrument descent rate. Application of a constant temporal advance of conductivity or temperature as is done with pumped CTDs is shown to produce unacceptable salinity spiking. With the descent rate of the UCTD reaching upwards of 4 dbar s−1, the effect of viscous heating of the thermistor is shown to produce a significant salinity error of up to 0.005 psu, and a correction based on previous laboratory work is applied. Correction of the error due to the thermal mass of the conductivity cell is achieved using a previously developed methodology with the correction parameters varying with instrument descent rate. Comparison of salinity from the UCTD with that from a standard shipboard, pumped CTD in side-by-side deployments indicates that the processed UCTD salinity is accurate to better than 0.01 psu.