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Fire Plumes and Flame Heights
Published in Björn Karlsson, James G. Quintiere, Nils Johansson, Björn Karlsson, Enclosure Fire Dynamics, 2022
Björn Karlsson, James G. Quintiere
Turbulence: Turbulent flows are fluid flows characterized by irregular fluctuations or mixing. The speed and direction of the fluid at a certain point will continuously change. Very small diffusion flames can be laminar, such as the flame on a candle. Larger diffusion flames are turbulent and will fluctuate with periodic oscillations with large eddies shedding at the flame edge (see Figure 4.1). The eddies, which are visible in turbulent plumes (more so in momentum-driven plumes than in buoyancy-driven ones), roll up along the outside of the plume and are a result of the instability between the hot flame and the cold air.
The Basic Concept for Microfluidics-Based Devices
Published in Raju Khan, Chetna Dhand, S. K. Sanghi, Shabi Thankaraj Salammal, A. B. P. Mishra, Advanced Microfluidics-Based Point-of-Care Diagnostics, 2022
A Reynolds number is a dimensionless quantity that helps in predicting the type of flow of a fluid. This concept was introduced in 1851 by George Stokes and popularized in 1883 by Osborne Reynolds, a British engineer, and physicist from the University of Manchester. A Reynolds number is the ratio of internal forces to viscous forces when a fluid is subjected to relative internal momentum owing to the differences in fluid velocities of individual layers. The detailed derivation of a Reynolds number is deduced in the latter half of the chapter. Re=InterialForceViscousForce=ρvDμ=uDv
Characterization Techniques of Phase Change Materials: Methods and Equipment
Published in Amritanshu Shukla, Atul Sharma, Pascal Henry Biwolé, Latent Heat-Based Thermal Energy Storage Systems, 2020
Karunesh Kant, Amritanshu Shukla, Atul Sharma
The rheometer is a laboratory device that is used to measure the technique in which a liquid, suspension, or slurry flows in response to applied forces. It is used for those fluids that cannot be defined by a single value of viscosity and therefore require more parameters to be set and measured than is the case for a viscometer. Viscosity is a measure of the resistance of a fluid, which is being deformed by the shear stress. Stress is the measure of internal force applied to an object. Shear stress is the stress that is applied parallel to the face of an object or material. In every day terms, viscosity is “thickness or internal friction.” Viscometer is an instrument used to measure the viscosity of a fluid. It measures the rheology of the fluid. Rheology is the study of the flow of matter, primarily in liquid state. The term rheometer comes from the Greek word rheo, meaning flow, and rheometer is a device for “measuring flow.”
Entropy approach of hydromagnetic Williamson nanofluid flow with Joule heating
Published in International Journal of Ambient Energy, 2023
Amir Yaseen Khan, Ibukun S. Oyelakin, Sabyasachi Mondal, Sharadia Dey
Prandtl (1904) introduced understanding boundary layer flow in fluid dynamics and provided a way to greatly simplify the constitutive equations of flow around an obstruction. For an excellent treatment of this subject refer to Schlichting (1951). Newtonian or non-Newtonian fluids are distinguished based on their viscosity at different shear rates. The fluids with constant viscosity for any shear rate are called Newtonian fluids while those fluids whose viscosity varies with shearing rates are called non-Newtonian fluids. For an excellent coverage of rheological behaviour of the fluids one can refer to Morrison (2001). Williamson (1929) derived a mathematical model for describing a class of fluids that were neither like plastics nor like Newtonian fluids. He documented that the flow of these fluids was very similar to plastics and only differed from them in that they did not possess a real yield value. Thus he named them pseudoplastic fluids. Today these fluids are known as Williamson fluids. They are also called shear-thinning fluids because with higher shear rates their viscosity decreases.
A time-fractional model of free convection electro-osmotic flow of Casson fluid through a microchannel using generalized Fourier and Fick’s law
Published in Waves in Random and Complex Media, 2022
Suleman Irshad, Farhad Ali, Ilyas Khan
Those fluids, obeying the Newton law of viscosity, are termed Newtonian fluids, while those fluids that do not obey it are called non-Newtonian fluids. Casson fluid is termed as the subclass of differential-type (non-Newtonian) fluid. Keeping in mind Casson fluid applications in engineering and science, many researchers have investigated Casson fluid in different rheologies. Khalid et al. [12] explored an unsteady magnetohydrodynamic flow taking the Casson fluid over a vibrating vertical channel. The result of applying magnetic field to the Casson fluid has been studied by Ali et al. [13]. Shaw et al. [14] investigate the flow of blood (Casson fluid) passing from the stenosed artery. They have analyzed the flow under the effect of body acceleration along with the magnetic field. A comparative work taking the flow of the Casson fluid with chemical reactions (homogenous-heterogeneous) is addressed by Khan et al. [15]. The MHD stagnation point flow effect is considered on a stretchable sheet. Sarojama et al. [16] elaborated on the MHD Casson fluid flow in a channel. Khan et al. [17] presented the generalized convective flow for the same fluid taking an upright channel. Mahanta and Shaw [18] presented a magnetohydrodynamic 3D flow of shear-thinning fluid over a porous sheet.
Aerodynamic design optimization of an automobile car using computational fluid dynamics approach
Published in Australian Journal of Mechanical Engineering, 2021
Ravi Kumar B, Nitesh Varshan M, Kannan T
Drag is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid (Anderson 2013). This can exist between two fluid layers (or surfaces) or between a fluid and a solid surface (Kundu et al. 2016). The components like diffuser, vortex generator, spoiler, tire cover and air ducts help in reducing drag and improving lift (Anish, Suthen, and Viju. 2017). Moussa, Yadav, and Fischer (2014) demonstrated that a properly designed rear suction mechanism can reduce drag by up to 9%. Gopal and Senthilkumar (2013) found that the main cause for aerodynamic drag in automotive vehicles is the separation of flow near the vehicle’s rear end. Anantha Raman and Hari (2016) researched and found that fairing the rear end of the vehicle reduces flow separation up to a greater extent and thereby reduces overall drag on the vehicle. Blocken and Toparlar (2015) presented a comprehensive flow analysis on a bicycle design and showed how a following car influences the drag on a cyclist. They concluded that the presence of wake region behind a moving body creates a large amount of drag. Hetawal, Mandar Gophane, and Mukkamala (2014) carried out an aerodynamic study of formula SAE car using the numerical method and found that reduction in wake region area leads to an increase in the overall performance of the car.