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Related Concept Videos

Irrotational Flow01:28

Irrotational Flow

Irrotational flow is characterized by fluid motion where particles do not rotate around their axes, resulting in zero vorticity. For a flow to be irrotational, the curl of the velocity field must be zero. This imposes specific conditions on velocity gradients. For instance, to maintain zero rotation about the z-axis, the gradient condition:
Bernoulli's Equation for Flow Along a Streamline01:30

Bernoulli's Equation for Flow Along a Streamline

Bernoulli's equation relates the energy conservation in a fluid moving along a streamline. The equation applies to incompressible and inviscid fluids under steady flow. For such a flow, Newton's second law is applied to a small fluid element, which experiences forces due to pressure differences, gravity, and velocity variations. The force balance leads to the following form of Bernoulli's equation:
Bernoulli's Equation for Flow Normal to a Streamline01:16

Bernoulli's Equation for Flow Normal to a Streamline

Bernoulli's equation for flow normal to a streamline explains how pressure varies across curved streamlines due to the outward centrifugal forces induced by the fluid's curvature. The pressure is higher on the inner side of the curve, near the center of curvature, and decreases outward to balance these centrifugal forces.
The pressure difference depends on the fluid's velocity and radius of curvature. The pressure variation is minimal in flows with nearly straight streamlines. However, the...
Gradually Varying Flow01:29

Gradually Varying Flow

Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...
General External Flow Characteristics01:26

General External Flow Characteristics

The study of external flow is essential for creating structures and objects that interact efficiently and safely with moving fluids, such as air or water. When a body is immersed in a flowing fluid, it experiences two primary forces: drag, which opposes motion along the flow direction, and lift, which acts perpendicular to the flow. The shape, size, and orientation of the object influence these forces.Streamlined and Blunt Bodies in External FlowObjects in fluid flow are classified as...
Laminar Flow01:27

Laminar Flow

Laminar flow represents a smooth, orderly fluid motion where particles move along parallel paths, resulting in minimal mixing between layers. Streamlined particle paths characterize this flow regime and occur under conditions where viscous forces dominate over inertial forces. The distinction between laminar, transitional, and turbulent flow is primarily determined by the Reynolds number, a dimensionless quantity calculated as:

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Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods
09:17

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods

Published on: April 23, 2018

Evolution of leftward flow.

Martin Blum1, Thomas Weber, Tina Beyer

  • 1University of Hohenheim, Institute of Zoology, Stuttgart, Germany. mblum@uni-hohenheim.de

Seminars in Cell & Developmental Biology
|December 6, 2008
PubMed
Summary
This summary is machine-generated.

Cilia-driven leftward flow is an ancient vertebrate trait crucial for body plan symmetry. Its absence in birds is likely a secondary loss, as it

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Area of Science:

  • Developmental Biology
  • Evolutionary Biology
  • Cell Biology

Background:

  • Asymmetric Nodal signaling is vital for body plan specification in deuterostomes.
  • Cilia-driven leftward flow is proposed as an ancestral mechanism for symmetry breakage in vertebrates.

Purpose of the Study:

  • To argue that cilia-driven leftward flow is an ancestral feature of vertebrates, potentially all deuterostomes.
  • To investigate the evolutionary loss of this flow mechanism in certain species.

Main Methods:

  • Review of existing literature on Nodal signaling, cilia function, and developmental patterns across deuterostomes.
  • Comparative analysis of embryonic development in various vertebrate groups, including fish, amphibians, mammals, and birds.

Main Results:

  • Leftward flow, mediated by monociliated epithelia derived from superficial mesoderm, occurs transiently during vertebrate gastrulation.
  • Birds, exemplified by chicks, lack superficial mesoderm and this flow, suggesting a secondary loss.
  • The presence of flow in fish, amphibians, and mammals supports its ancient origin.

Conclusions:

  • Cilia-driven leftward flow is likely an ancestral chordate and possibly deuterostome characteristic.
  • The absence of flow in birds represents a secondary evolutionary event, not a primitive condition.