Fluid Mechanics: A Study Guide

Fluid Mechanics I: Study Guide is written as main reference for students who take the subject of Fluid Mechanics I. Contents of this study guide are organized into chapters, and are arranged in the sequence they should be read. This is because knowledge learnt in the earlier chapters will be applied in the latter. One possible exception is to study dimensional analysis in Chapter 11 before the other chapters as it stresses more on algorithm rather than on the aspects of Fluid Mechanics. There are total eleven chapters. Chapters 1 and 2 are introduction to fluid and its properties. Chapter 3 to 5 discuss fluid phenomena under static conditions. These include fluid pressure in Chapter 3 and forces cause by the fluid pressure in Chapter 4 and 5. However, Chapter 5 covered specifically on topics about buoyancy and stability. chapter 6 to 10 discuss fluid phenomena under dynamic conditions. Types of flow and the way to quantify it are introduced in Chapter 6. Chapters 7 and 8 discuss about flow energy equations and its application. In Chapter 9, forces produced in a flowing fluid are presented. Whilst the previous chapters dealt with flow of idea fluid, Chapter 10 dealt with real fluid phenomena and methods used in solving simple pipe flow problems

The Effect Of Building Shape Modification On Wind Pressure Differences For Cross-Ventilation Of A Low-Rise Building

The present study investigates the effect of alteration in the building shape due to some common remodelling practice on the wind pressure differences Δp for cross-ventilation of a semi-detached low-rise building using Computational Fluid Dynamics (CFD). A commercial code ANSYS CFX was employed to solve the flow governing equations. The standard k −ε, renormalisation group (RNG) k −ε and Shear Stress Transport (SST) turbulent models were adopted for comparison and the computed velocity was validated against full-scale measurement data. Results computed with these three turbulent models were able to capture the trend of the measured wind speed at the chosen locations with appreciable discrepancy level. Maximum wind pressure differences Δp for cross-ventilation under the effect of building remodelling was calculated based on the CFD results. At the windward side, highest Δp was provided when expansion is made on the kitchen zone of the back neighbouring house. The house with fencing provided the lowest Δp value. In general, for all types of building remodelling, Δp value for houses on the windward side was higher by 447% (on the average Δp value) compared to the houses on the leeward side

Yaw angle effect on the aerodynamic performance of hatchback vehicle fitted with wing spoiler

Research on spoiler available to date was mainly done to optimize the performance of spoiler in non-zero yaw condition. However, the effect of spoiler is most needed during cornering to ensure the stability of the vehicle. Therefore, this study aims to inspect the effect of yaw angles change on the aerodynamic performance of the NACA 0018 wing spoiler and the subsequent influence on the flow characteristics of the hatchback vehicle. Computational Fluid Dynamics (CFD) has been applied to model the flow. Comparison between numerically obtained results and experimental data was done to validate the CFD method. The findings show that both the drag coefficient, Cd, and lift coefficient, Cl have increased with increasing yaw angle. However, the spoiler has performed in favor of reducing the Cd and Cl even with increasing yaw angle. The averaged proportion contributions from the spoiler to the overall Cd and Cl are 2.7% and 4.1%, respectively. The other body parts that have contributed to the Cd and Cl reductions were the base and slant, and the roof

Yaw Angle Effect On The Aerodynamic Performance Of Hatchback Vehicle Fitted With Wing Spoiler

Research on spoiler available to date was mainly done to optimize the performance of spoiler in non-zero yaw condition. However, the effect of spoiler is most needed during cornering to ensure the stability of the vehicle. Therefore, this study aims to inspect the effect of yaw angles change on the aerodynamic performance of the NACA 0018 wing spoiler and the subsequent influence on the flow characteristics of the hatchback vehicle. Computational Fluid Dynamics (CFD) has been applied to model the flow. Comparison between numerically obtained results and experimental data was done to validate the CFD method. The findings show that both the drag coefficient, Cd, and lift coefficient, Cl have increased with increasing yaw angle. However, the spoiler has performed in favor of reducing the Cd and Cl even with increasing yaw angle. The averaged proportion contributions from the spoiler to the overall Cd and Cl are 2.7% and 4.1%, respectively. The other body parts that have contributed to the Cd and Cl reductions were the base and slant, and the roof

Heat Sealability Of Laminated Films With LLDPE And LDPE As The Sealant Materials In Bar Sealing Application

The heat sealability of laminated films with linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) as the sealant materials was investigated. A laboratory heat sealer was used to study the response of laminated films to temperature, time, and pressure. Platen temperature was confirmed as primary factor in controlling heat-seal strength. Dwell time must be sufficiently long to bring the interfacial temperature to a desired level. When the desired heat-seal strength has been achieved, further increase of dwell time did not improved heat-seal strength. Platen pressure had little effect above the level required to flatten the materials for good contact. Bar sealing process window for each sample were developed. The optimum combination of platen temperature and dwell time for each laminated film can be obtained in the respective process windows. Strength of heat-seal and its failure modes are closely related. Plateau initiation temperature closely corresponds to the final melting point of sealant materials. Relatively higher platen temperature was required to seal laminated films with lower thermal conductance. Required dwell time corresponds closely to the heat flow rate of bar sealing process. Laminated films made from extrusion lamination process provided lower level of achievable heat seal strength when compared with the laminated films made from dry-bond lamination process

Effects Of Transient Aerodynamics On Vehicle Stability: A Large Eddy Simulation Analysis

The present study investigated the extent to which the results obtained from simple bluff body model, regarding pitching stability, can be applied to real vehicle aerodynamics. The investigation was carried out using a large eddy simulation method with vehicle-motion-airflow dynamic coupling capability. The aerodynamic damping coefficient and mechanism obtained from realistic sedan-type vehicle model cases are found similar to the one for simple body model cases. These agreements deduce that the use of simple body model in automotive aerodynamic research is justifiable

Aerodynamic Pitching Stability Of Sedan-Type Vehicles Influenced By Pillar-Shape Configurations

The present study investigated the aerodynamic pitching stability of sedan-type vehicles under the influence of A- and C-pillar geometrical configurations. The numerical method used for the investigation is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was employed to realize the prescribed pitching oscillation of vehicles during dynamic pitching and fluid flow coupled simulations. The trailing vortices that shed from the A-pillar and C-pillar edges produced the opposite tendencies on how they affect the aerodynamic pitching stability of vehicles. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation of vehicle, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A- and C-pillars configurations. The underlying aerodynamic damping mechanism has been verified through flow visualization of phase-averaged results

Heat-Seal Strength Analysis Of Laminated Films With LLDPE And LDPE Sealant Materials In Bar Sealing Application

The heat-seal strength and failure modes of laminated films with Linear Low Density Polyethylene (LLDPE) and Low Density Polyethylene (LDPE) as the sealant materials were investigated. Heat-seal strength increases with platen temperature for all samples. The maximum achievable heat-seal strength for laminated film using LDPE and LLDPE as sealant material is 0.598 N/mm and 4.02 N/mm, respectively. Four failure modes were observed, namely, the peeling mode, tearing mode, delamination mode and combination of tearing and delamination mode failures. Strength of heat-seal and its failure modes are closely related. Heat-seal strength achieved under tearing mode failure is the highest, follow by heat-seal strength achieved under delamination mode failure, and the heat-seal strength achieved under peeling mode failure is the lowest. Corresponding platen temperature TC and heat-seal strength SSC where acceptable heat-seal begins to be made weree 118, 114 and 108 ºC, and 2.82, 2.38 and 0.48 N/mm for sample #1, #2 and #3, respectively

Numerical Analysis Of The Effects Of Transient Aerodynamics On Driving Stability

The present study investigated the effects of transient aerodynamic forces on driving stability of road vehicle. The investigation was carried out using large eddy simulation (LES). To facilitate the investigation, two vehicle models with distinct upper body geometries were developed. The models adopted the characteristic geometries of upper body of real sedan-type vehicles with distinct pitching stability behavior. To probe the dynamic response of the models, a forced-sinusoidal-pitching oscillation is imposed on them during the LES. Accordingly, the models undergo pitching oscillation in a similar manner to the rear-ride-height fluctuation of real vehicles. To allow quantitative analysis on the stability characteristic of models, a parameter termed aerodynamic damping coefficient is introduced. The coefficient quantifies the work done by aerodynamic pitching moment on the models during pitching oscillation. For validation of the LES method, flow structures around the models obtained by stationary LES were compared to the wind tunnel measurements. The comparison shows good agreement. Meanwhile, the dynamic LES results show higher aerodynamic damping in the model with rounded front pillar configuration, by about 22.3%. The Underbody has the highest contribution to the total aerodynamic damping, which was up to 69%. However, the difference between the aerodynamic damping of models with distinct front and rear pillar configurations mainly depends on the trunk-deck contribution

On The Aerodynamic Damping Mechanism Of Vehicle Pitching Stability Using Large Eddy Simulation

Large eddy simulation was conducted to investigate the pitching stability characteristic of notchback-type vehicle. In this paper, two simplified vehicle models represent the notchback of different pitching stability characteristics were used. Numerical method adopted was validated by comparing the simulation result with wind tunnel data. To probe the dynamic response of the models, forced-sinusoidal-pitching oscillation is imposed and the resulting pitch moment is phase averaged, and decomposed into the stationary, quasi-stationary, and dynamic components for assessment. Vehicle model of higher aerodynamic damping is found to exhibit two-dimensional flow structure above the central region of its trunk deck, whereas vehicle model of lower aerodynamic damping is associated with strong cross flow and upwash circulatory flow structure. The outcome of this work demonstrates how unsteady aerodynamics can be exploited for the control of vehicle’s straight ahead stability