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Introduction
Published in Ahlam I. Shalaby, Fluid Mechanics for Civil and Environmental Engineers, 2018
The characteristics/properties of a fluid system, along with the fluid kinematics and fluid dynamics, will determine the type of flow (see Chapter 3 for detailed discussion). First, a flow may be classified as internal flow (pipe or open channel) or external flow (flow around an object), depending upon the use of energy or work to move the fluid. Second, an internal flow may be classified as a pressure (pipe) flow or a gravity (open channel flow), depending upon whether a hydraulic gradient or gravity caused the flow. Third, a flow may be real (viscous) or ideal (inviscid), depending upon the value assumed for the fluid viscosity. A real flow may be subdivided into laminar or turbulent flow, depending upon the value of the Reynolds number, R = ρvL/μ. Furthermore, real fluids may be divided into Newtonian and non-Newtonian fluids. Fourth, a flow may be compressible (pressure flow) or incompressible (pressure flow or gravity flow), depending upon the spatial and/or temporal variation in the fluid density. Fifth, a flow may be spatially varied (nonuniform) or spatially uniform, depending upon the spatial variation in fluid velocity (convective acceleration). Sixth, a flow may be unsteady or steady, depending upon the temporal variation in the fluid velocity (local acceleration). And, seventh, a flow may be one-, two-, or three-dimensional, depending upon the assumption of spatial dimensionality.
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
The Bernoulli equation may be used to predict pressure variations in external flow over objects and to design instrumentation for measuring pressure and velocity. Stagnation pressure is sensed by a totalhead tube where V = 0. For this situation the Bernoulli equation reduces to p0=p+12ρV2
Fluid Mechanics
Published in Keith L. Richards, Design Engineer's Sourcebook, 2017
External flow covers the flow that is outside a boundary, body or conduit. Examples of these types of flow include immersed bodies, airflow around buildings and flow over aircraft wings and suspension bridges and around automobile vehicles.
Effect of particle size and bed height on the characteristic of a fluidized bed dryer
Published in Cogent Engineering, 2020
Eflita Yohana, Mohammad Tauviqirrahman, Awallina Ani Sayekti, Kwang-Hwan Choi, Vita Paramita
The most fundamental characteristic of a fluidized bed dryer is the relationship between pressure drop and gas velocity (superficial gas velocity).The flow of gas that moves up and down the material grains creates a drag force (Fd) and buoyancy force (buoyancy force) on the particle. In the physical model adopted here, the air flow that passes through solid objects (i.e. particles) will have the drag force. External flow is influenced by fluid flow and the geometry of the object. The relative air velocity in objects that are enveloped in air flow and moving away from objects (outside the boundary layer) is called free stream velocity (Cengel & Cimbala, 2018). Increasing the speed of gas entering the fluidized bed causes an increase in pressure drop (∆P) and drag force on the particles. When drag force and buoyancy force generated by the velocity of gas entering pounding particles is balanced, the gravitational force (Fg), or the weight of the static bed, will experience a fluidization phenomenon. Figure 1 shows the balance of forces acting when particles have a substantial impact on the air flow.