China
Africa
Explore chapters and articles related to this topic
Physical and Chemical Factors Governing the Behavior of Physiological Regulators and Control Systems
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
Several physiological systems involve fluid dynamics in their descriptions. These include the respiratory system, the regulatory systems for intraocular pressure and cerebrospinal fluid pressure, and systems involving the circulatory system (e.g., blood pressure regulation, short term and long term). In the simplified descriptions of fluidic systems below, we assumed that laminar flow conditions are present (i.e., there is no turbulence). Laminar flow is generally present when the Reynolds number is less than 1000. The Reynolds number of a fluid flowing in a cylindrical tube is given by: () Re=ρv¯rη
Design and Analysis
Published in Quamrul H. Mazumder, Introduction to Engineering, 2018
If all the fluid particles are moving in paths parallel to the overall flow direction, the flow is called laminar flow. This occurs when the Reynolds number is less than approximately 2100. Laminar flow is typical when the flow channel is small, the velocity is low, and the fluid is viscous. Laminar flow is illustrated by pouring viscous fluid such as honey, shampoo, or engine oil.
Convection
Published in Greg F. Naterer, Advanced Heat Transfer, 2018
The structure of a flat plate boundary layer involves a laminar portion from the leading edge up to a transition point, xc (at Rex = Ux/ν ≈ 5 × 105), followed by a transition region and turbulence thereafter. Laminar flow occurs when the fluid moves in parallel layers without disruption between the layers. This typically occurs at low velocities where the fluid moves without lateral mixing. In contrast, turbulence occurs at higher velocities when the fluid motion is characterized by chaotic changes in pressure and flow velocity. Following transition to turbulence, the enhanced mixing in the fluid leads to an increase of cross-stream velocity fluctuations and the turbulent boundary layer grows more rapidly. There are three distinct regions within the turbulent boundary layer—an inner viscous sublayer (where molecular diffusion is dominant); an overlap or buffer layer; and an outer layer where turbulence effects are dominant.
Investigation of suspended particle size effects on clogging of soil filters under laminar flow
Published in European Journal of Environmental and Civil Engineering, 2022
Sahar Banihashem, Mohsen Karrabi
Laboratory conditions for Darcy flow were studied using the dimensionless Reynolds number (Re) (Beach et al., 2005; Karrabi et al., 2011). Reynolds number expresses the inertial forces to viscous ratio, as a measure to differentiate laminar flow at low speeds and turbulent flows. Reynolds number for the porous medium is shown by Equation (1). where: Q denotes flow rate, A indicates cross-section, dp presents average grain diameter of the porous medium, Ρ is fluid density, µ fluid dynamic viscosity and φ denotes porosity in a layer between the two sampling ports (Fleming et al., 1999). When Re <10, flow will be laminar (Karrabi et al., 2011). Dynamic viscosity of water was considered 10−3 kg/m s at a temperature of 20 °C.
Continuous microwave drying of germinated brown rice: Effects of drying conditions on fissure and color, and modeling of moisture content and stress inside kernel
Published in Drying Technology, 2021
Liuyang Shen, Lei Wang, Chenyang Zheng, Chenghai Liu, Yong Zhu, Hui Liu, Chai Liu, Yongkun Shi, Xianzhe Zheng, Hao Xu
In continuous microwave drying of GBR, the airflow with room temperature entered the drying cavity at a set speed (or flow rate). The Reynolds number (Re) expressed by Equation (23), is a dimensionless number to measure the ratio of fluid inertial force to viscous force, and it is used as the criterion for judging laminar flow and turbulence. where is the fluid (air) density (kg/m3), is the dynamics viscosity of fluid (), is the characteristic velocity of the airflow (m/s), L is the characteristic length of material layer (6.4 m).
Geology and field relations of the Wilsons Promontory batholith, Victoria: multiple, shallow-dipping, S-type, granitic sheets
Published in Australian Journal of Earth Sciences, 2018
In the NPBM, features that resemble scour and fill have been noted above. In explanations for the formation of such structures, analogies are commonly drawn with sedimentary erosional and depositional features (e.g. Paterson et al., 2016). However, since the formation of scour and fill, in sedimentary environments, requires turbulent flow, these structures in the granitic systems cannot have been formed in that way. Indeed, the example shown in Paterson et al. (2016, figure 12f) is unconvincing as scour and fill. It rather resembles a warping downward of a phenocryst-bearing layer, perhaps owing to loading from above or magma flow over an uneven substrate. Surface roughness disturbs laminar flow and causes it to undulate. This undulating but still laminar flow might cause eddy formation, allow deposited crystals to be re-entrained into the flow and perhaps mimic turbulent scour structures. This effect is most likely to occur in less viscous magmas (Petford & Mirhadizadeh, 2017) but local contact geometry is a critical parameter, and the effect may well occur in granitic systems as well (N. Petford, written comm. 2018).