Computational one-factor investigation on the effect of sonication parameters in biomass pretreatment

The application of ultrasonic irradiation has been proven as a clean and efficient approach for biomass pretreatment process. However, the effects of sonication parameters on the performance of biomass pretreatment are not well discussed due to its physical complexity. The current work aims to model Rayleigh-Plesset equation (RPE) to investigate how the fluid property of biomass-water (surface tension and dynamic viscosity) and sonication parameters (sonication frequency and power) influence the growth and bounce of microbubbles. The collapsing temperature, collapsing pressure, and shock pressure are computed. Moving Least Squares and Multivariable Power Least Squares Method are applied for multivariate investigation. The results revealed that fluid properties are more significant than sonication parameters

Numerical modelling of convective wave using fractional-step method

Wave equation is often solved independently without involving Continuity and momentum equations and this implies that the numerical simulation is restricted to wave phenomenon in static fluid. Meanwhile the available wave models are more suitable for the case in which the convective effect outweighs the local wave fluctuation. However, there are many fluid dynamics phenomena which involves equally significant effect of convective flow and wave disturbance, such as mountain waves, strong aeroacoustics wave and strong ocean waves. These flows need to be simulated by computational coupling. We have developed a solver using fractional step method for the construction of convective wave coupling algorithm. In our implementation, we model a flow across the wave-excited lid driven cavity as our case study, in which the model is to imitate the aerodynamic mountain wave. We found that the convective wave ratio plays a great role in affecting the velocity field of the fluid domain

A numerical study of heat transfer to turbulent separation nanofluid flow in an annular passage

The separation and the reattachment of nanofluid flow through a sudden expansion in an annular passage have been studied. ANSYS FLUENT was deployed to simulate the effect of separation of nanofluid flow on the local and average convection heat transfer in an annular passage. The outer tube was made of aluminium with internal diameter of 83 mm and horizontal length of 600 mm, subjected to a constant wall heat flux. The investigation was performed with varying Reynolds number ranging from 5000 to 25000, heat flux from 719 W/m2 to 2098 W/m2, and the enhancement of step heights expanding from 0 mm (d/D=1) to 18.5 mm (d/D=1.8). The increase of flow velocity results in the sudden drop of the surface temperature in proximity to the pipe entrance, followed by gradual increment of surface temperature along the pipe. The minimum surface temperature could be obtained at flow reattachment point. The position of the minimum temperature point is independent on the inlet flow velocity. In general, the average Nusselt number increases with the increase of Reynolds number

On stability of time marching in numerical solutions of rayleigh-plesset equation for ultrasonic cavitation

Ultrasonic irradiation approach has become one of the most popular methods applied in chemical processing including lignocellulosic biomass pretreatment and industrial cleansing. The phenomenon of ultrasonic cavitation can be indeed delineated via the Rayleigh-Plesset equation (RPE), which governs the transient radius of the bubble. Nonetheless, the time marching in the numerical solutions for RPE is highly unstable, which cannot be assured using von Neumann analysis. High sensitivity of RPE to time step may lead to extremely long computational time. The lack of numerical investigation into the time stepping issue of RPE has hindered in-depth simulation of ultrasonic cavitation. Therefore, the purpose of this paper is to investigate the stability criterion of time stepping for RPE in different time progression schemes, namely Euler explicit, 2nd order Taylor’s method, 4th order Runge-Kutta, Runge-Kutta Fehlberg and Cash-Karp Runge-Kutta method. A simple modified adaptive time step method and a independence study has been introduced in this paper for fast, stable and accurate computation of RPE. Compared with the traditional constant time marching method, the new model is able to improve the computational cost significantly without affecting the time marching stability and resolution of the results. Among the investigated method, Runge-Kutta family solvers have higher computational accuracy, with the cost of higher critical a value. The model is also applied to compute the pressure and temperature hike during bubble collapse due to different sonication power. The simulation results show that the ultrasonic irradiation with higher sonication power could produce a higher energy to break the lignocellulose wall

Preliminary investigation on the disruption of microalgae cell wall using vortex induced vibration (VIV)

Scenedesmus sp. is industrially known for its high lipids content that can be used in biofuels production. Most of the conventional mechanical methods to disrupt the microalgae cell wall use high frequency approaches. The conventional high frequency methods have few disadvantages which are high energy consumption, high cost and application of solvents which are the cause of environmental pollution. In this paper, a low frequency method called vortex induced vibration (VIV) is proposed to replace the conventional mechanical methods to disrupt microalgae cell wall. An experimental rig has been designed and fabricated for this experiment. Based on the experiment, the result shows that VIV method has the possibility to break microalgae cell wall since the turbidity decrease throughout the days

Principal component analysis on meteorological data in UTM KL

The high usage of fossil fuel to produce energy for the increasing demand of energy has been the primary culprit behind global warming. Renewable energies such as solar energy can be a solution in preventing the situation from worsening. Solar energy can be harnessed using available system such as solar thermal cogeneration systems. However, for the system to function smoothly and continuously, knowledge on solar radiation’s intensity several minutes in advance are required. Though there exist various solar radiation forecast models, most of the existing models requires high computational time. In this research, principal component analysis were applied on the meteorological data collected in Universiti Teknologi Malaysia Kuala Lumpur to reduce the dimension of the data. Dominant factors obtained from the analysis is expected to be useful for the development of solar radiation forecast model

Dynamic behaviours of damaged stability for floating energy storage unit after accidental collision

The transient dynamic behaviour of floating energy storage unit (FESU) is a result of coupling between three non-linear effects, which are sloshing of floodwater, wave loading, and FESU dynamics. The coupling of these effects would result in the catastrophic failure of the FESU in extreme conditions. Computational Fluid Dynamics (CFD) has shown that it holds great potential in solving the problem in the time domain, which is suitable for the transient stage. In this study, CFD simulation of damaged stability was conducted by using OpenFOAM to determine the dynamic response of FESU under the effects of floodwater and wave in transient flooding. OpenFOAM CFD simulation was conducted for the flooding of barge shaped FESU with different water inlet and air outlet sizes in still water condition followed by damaged stability in Stokes’ fifth-order beam wave and head wave condition. Dynamic responses of FESU, such as roll, pitch, heave, and floodwater volume flow rates were determined using the dynamic meshing solver of OpenFOAM. Simulation results showed similarity to experimental results within the time frame of 16 seconds. Reduction in water inlet area and air outlet area decreased the flooding time and flow rate of flood water. The amplitude of vibration of roll and pitch motion increased as the flood water volume was increased due to the force of floodwater exerted on the wall. Sloshing effects also caused the model to roll and pitch in secondary vibrational motion. Due to the coupling effect of the three non-linear criteria, the inflow and outflow of floodwater changed with time, which concludes that transient effects should not be ignored in the damaged stability assessment of FESU

Velocity analysis on moving objects detection using multi-scale histogram of oriented gradient

An autonomous car is a one-of-a-kind specimen in today's technology. It is an automatic system in which most of the duties that humans undertake in the car can be done automatically with minimum human supervision for road safety features. Moving automobile detections, on the other hand, are prone to more mistakes and can result in undesirable situations such as minor car wrecks. Moving vehicle identification is now done using high-speed cameras or LiDAR, for example, whereas self-driving cars are produced with deep learning, which requires much larger datasets. As a result, there may be greater space for improvement in the moving vehicle detection model. This research intends to create another moving car recognition model that uses multi-scale feature-based detection to improve the model's accuracy while also determining the maximum speed at which the model can detect moving objects. The recommended methodology was to create a lab-scale model that can be used as a guide for video and image capture on the lab-scale model, as well as the speed of the toy vehicles captured from the Arduino Uno machine before testing the car recognition model. According to the data, Multi-Scale Histogram of Oriented Gradient can recognize more objects than Histogram of Oriented Gradient with higher object identification accuracies and precision

Reynolds number-strouhal number relationship for cylindrical bluff body with variation of aspect ratio in high Reynolds number

The effect between Reynolds number and bluff body aspect ratio to the flow parameters such as Strouhal number and drag coefficient are studied. The range of Reynolds number applied is within 10000 and 200000 while three aspect ratio (Ar) where Ar = 1.0, 1.5 and 2.0 are implemented. Finite volume method with the aid of ANSYS CFX codes is deployed using the turbulence SST model. Equations of Re-St relationship for Ar 1.0 and 1.5 are then hypothesized as well in this paper for the range of 10000<Re<100000

Semi-Analytical Method for Unsymmetrical Doublet Flow Using Sink- and Source-Dominant Formulation

Potential flow formed by doublet flow has been well applied in environmental applications and geothermal designs such as reservoir and fuel injectors. Most of the doublet flow is assumed based on the sink and source with equivalent strength and distance from the origin, forming the well-known Rankine oval structure when a far-field flow is superposed. A semi-analytical method is formulated to systematically investigate the unsymmetrical doublet flow with different strengths of sink and source. The general mathematical expression for unsymmetrical doublet flow is derived analytically before the streamline and the potential line can be visualised via a numerical approach. The results revealed that the doublet flows altered the Rankine oval structure to form aerofoil-like geometry. When the far-field flow interferes with the general Doublet configuration, unique flow structures such as convex, concave, and various wing shapes could be generated. The current study provides new insight on producing aerodynamic curves for the design of bio-inspired structures