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Related Concept Videos

Pressure Variation in a Fluid at Rest01:11

Pressure Variation in a Fluid at Rest

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In a fluid at rest, the pressure at any point beneath the fluid surface depends solely on the depth, not on the container's shape or size. This principle, known as hydrostatic pressure, arises because, in stationary fluids, there is no acceleration, meaning the forces within the fluid balance out. Only vertical forces, caused by the weight of the fluid above, contribute to pressure changes with depth.
When measuring pressure at two different levels within the fluid, the difference in...
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Measurement of Fluid Pressure01:16

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Fluid pressure is commonly measured using devices called manometers, which rely on liquid columns to indicate pressure differences. The height of a liquid column in a manometer reflects the pressure exerted by the fluid, providing a simple yet effective means of measurement. Different types of manometers serve specific purposes based on their configurations and the type of fluids involved.
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Velocity and Acceleration in Steady and Unsteady Flow01:11

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In fluid mechanics, velocity and acceleration are key concepts for analyzing particle motion in both steady and unsteady flow. Consider a fluid particle moving along a pathline, where its velocity depends on its position and time. The particle's acceleration is obtained by differentiating the velocity with respect to time.
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Velocity Potential01:20

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In steady, incompressible flow through a long, straight pipe with a uniform cross-section, the flow in the central region (far from the pipe walls) is irrotational. This irrotational nature means that fluid particles do not rotate around their axes, and a scalar function called the velocity potential, represented by ϕ, can be used to describe their movement. In irrotational flows, the velocity field V is defined as the gradient of the velocity potential:
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Fluid Pressure over Flat Plate of Variable Width01:02

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When a flat plate is submerged in a fluid, the fluid exerts pressure on the plate. This pressure can lead to many different phenomena, including drag and buoyancy. To understand the behavior of the fluid over a flat plate of variable width, it is essential to analyze the distribution of the pressure exerted.
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High-speed Particle Image Velocimetry Near Surfaces
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Near-ambient pressure velocity map imaging.

Tzu-En Chien1, Lea Hohmann1, Dan J Harding1

  • 1Department of Chemical Engineering, KTH Royal Institute of Technology, Stockholm 100 44, Sweden.

The Journal of Chemical Physics
|July 22, 2022
PubMed
Summary

A new Near-Ambient Pressure Velocity Map Imaging (NAP-VMI) instrument bridges the pressure gap in surface science. This tool enables studying chemical dynamics at higher pressures, advancing catalysis research.

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Area of Science:

  • Surface Science
  • Chemical Kinetics
  • Catalysis

Background:

  • Studying surface reactions at higher pressures is crucial for catalysis but challenging due to vacuum requirements.
  • A significant "pressure gap" exists between traditional surface science techniques and real-world catalytic conditions.
  • Existing methods struggle to analyze molecular dynamics under near-ambient pressure conditions.

Purpose of the Study:

  • To introduce and validate a novel Near-Ambient Pressure Velocity Map Imaging (NAP-VMI) instrument.
  • To enable the study of molecular beam surface scattering and chemical reaction dynamics at pressures closer to applied catalysis.
  • To bridge the gap between ultra-high vacuum surface science and higher-pressure catalytic processes.

Main Methods:

  • Development of a NAP-VMI instrument utilizing specialized ion optics to guide ions through an aperture.
  • The aperture effectively separates a high-pressure ionization region from the vacuum detector region.
  • Velocity mapping of ions to analyze scattering dynamics and photodissociation.

Main Results:

  • Demonstrated performance of NAP-VMI using N2O photodissociation and N2 scattering from Pd(110).
  • Comparison of results obtained under vacuum and near-ambient pressure (1 x 10^-3 mbar) conditions.
  • Successful operation of the instrument at pressures previously inaccessible for VMI.

Conclusions:

  • The NAP-VMI instrument is a viable new tool for studying surface dynamics at near-ambient pressures.
  • This technique can significantly advance the understanding of chemical reaction dynamics and kinetics in catalysis.
  • NAP-VMI has broad applicability, including potential use in photoelectron spectroscopy and liquid microjet scattering experiments.