Flow Velocity Distribution in Roughness Sublayers
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Solution Overview
Problem
Current methods fail to accurately determine flow velocity distribution in the roughness sublayer, which is crucial for understanding river bed evolution, atmospheric pollutants transport, and wind resource utilization, due to the complexity of simulating and measuring flow characteristics in this zone.
Innovation Solution
A method utilizing a variable-slope circulating flume system and an Acoustic-Doppler Velocimeter to simulate and measure flow velocity distribution in the roughness sublayer, dividing it into near-bottom, penetration, and free flow regions, with cylindrical aluminum rods simulating roughness elements and adjusting flow parameters for accurate data collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used in the roughness sublayer, then measurement simplicity is maintained, but measurement precision deteriorates due to the complex flow characteristics and roughness elements
Solution Approach 1:
The roughness sublayer is segmented into three distinct zones (near-bottom layer, mixing layer, and free flow region) based on flow characteristics. This segmentation allows for zone-specific measurement strategies and theoretical analysis, improving measurement precision by addressing the complexity of each zone separately rather than treating the entire sublayer uniformly.
Solution Approach 2:
An Acoustic-Doppler Velocimeter (ADV) is introduced as an intermediary measurement device that can accurately capture flow velocity in the complex roughness sublayer environment. The ADV serves as a mediator between the complex flow field and the measurement system, enabling precise velocity measurements without requiring direct contact with roughness elements or complex probe arrangements.
2Measurement precision
If the roughness sublayer is studied as a whole, then study simplicity is maintained, but measurement precision deteriorates due to the heterogeneous flow characteristics in different zones
Solution Approach 1:
The roughness sublayer is divided into three zones: near-bottom layer (0<z<h), mixing layer (h<z<hp), and free flow region (hp<z<ho). Each zone has distinct flow characteristics and requires different measurement approaches. This segmentation enables precise velocity distribution measurement in each zone while providing a systematic framework for understanding the heterogeneous flow structure.
Solution Approach 2:
Different measurement and theoretical approaches are applied to different zones within the roughness sublayer. The near-bottom layer uses specific velocity scales and length scales appropriate for roughness-dominated flow, while the free flow region uses different parameters. This local quality approach ensures that each zone is measured and analyzed with methods optimized for its specific flow characteristics.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables quick and accurate measurement of flow velocity profiles in the roughness sublayer, providing theoretical foundations for refined simulations of river and terrestrial air flows, and aiding in the study of river bed evolution and pollutant transport.
Implementation Method 1
the flow-measuring system uses an Acoustic-Doppler Velocimeter (ADV) to measure the flow velocity
Data Source
AI summary
A method for determining flow velocity distribution in the roughness sublayer is provided, which uses the experimental device that includes a variable-slope circulating flume system and a flow-measuring system, the variable-slope circulating flume system is used to study flow in the roughness sublayer, and the flow-measuring system is used to measure flow velocity in each zone in the flume. In the variable-slope circulating flume, the method according to the invention uses cylindrical aluminum rods to simulate large-scale roughness elements, and the submergence, the average bulk flow velocity and the distribution density of roughness elements are changed.