Wind Stress Coefficient Expression for Lake Simulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wind stress coefficient expressions in numerical simulation studies primarily consider only average wind speed, ignoring the impacts of fetch and water depth, leading to uncertainty and inaccuracy, especially in waters with limited fetch and depth, and fail to account for wave-current characteristics.
Innovation Solution
A method and system for expressing wind stress coefficient that comprehensively considers average wind speed, fetch, and water depth, using dimensionless parameters like Froude and Reynolds numbers to represent interaction strengths, and a nonlinear logarithmic function to construct a more accurate expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional wind stress coefficient expression considering only average wind speed is used, then the expression is simple, but the simulation accuracy and reliability deteriorate
Solution Approach 1:
The patent transforms the wind stress coefficient expression from a single-parameter form (Cd=f(u10)) to a multi-parameter form (Cd=f(u10,F,d)) by introducing fetch F and water depth d as additional parameters. This parameter expansion allows the expression to account for more physical factors affecting wind-wave-current interaction, thereby improving simulation reliability while maintaining reasonable complexity through dimensionless parameter formulation.
Solution Approach 2:
The patent creates a composite expression structure that integrates multiple physical parameters (wind speed, fetch, water depth) into a unified wind stress coefficient model. By combining these different parameters in a dimensionless framework, the expression achieves both comprehensiveness and simplicity, resolving the contradiction between expression complexity and simulation reliability.
2Ease of operation
If a wind stress coefficient expression considering only wind speed is used, then the expression is easy to operate, but the measurement precision and simulation accuracy deteriorate
Solution Approach 1:
The patent enhances the expression's precision by adding fetch and water depth parameters to the conventional wind speed-only model. The dimensionless parameter formulation (using Froude number and relative water depth) maintains ease of operation while significantly improving simulation accuracy, especially for lakes and coastal waters with limited fetch and depth.
Solution Approach 2:
The patent transitions from a one-dimensional wind speed parameter to a three-dimensional parameter space (wind speed, fetch, water depth). This dimensional expansion captures the complex physics of wind-wave-current interaction more accurately while the dimensionless formulation keeps the expression practical and easy to use in numerical simulations.
3Adaptability or versatility
If existing wind stress coefficient expressions are used for waters with limited fetch and depth, then the expression is universally applicable, but the simulation accuracy deteriorates
Solution Approach 1:
The patent develops a specialized expression formulation that accounts for local characteristics of waters with limited fetch and depth. By incorporating fetch F and water depth d as explicit parameters, the model adapts to local conditions rather than applying a universal wind speed-only relationship, thereby improving accuracy for specific water body types while maintaining broad applicability through dimensionless parameters.
Solution Approach 2:
The patent modifies the expression parameters to include fetch and water depth, making the model adaptable to different water body characteristics. The dimensionless parameter formulation (Froude number, relative water depth) ensures the expression remains universally applicable across different scales and conditions while accurately representing local physics.
4Device complexity
If a conventional wind stress coefficient expression is used, then the model is simple, but it cannot reflect wave-current characteristics and saturation effect
Solution Approach 1:
The patent introduces fetch and water depth parameters to capture wave-current interaction characteristics that are absent in conventional models. These additional parameters enable the expression to reflect the saturation effect at high wind speeds and the developing stage characteristics in limited fetch/depth conditions, improving reliability without excessive complexity.
Solution Approach 2:
The patent creates a dynamic expression that adapts to different wind-wave-current interaction stages (developing and mature stages) through the fetch and water depth parameters. The model dynamically adjusts the wind stress coefficient based on the relative importance of these parameters under different conditions, accurately representing the saturation effect and stage-specific 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
The proposed method provides a more realistic and adaptable wind stress coefficient expression, improving simulation accuracy by accounting for the nonlinear relationships between wind speed, fetch, and water depth, and is applicable to various water bodies, including those with limited fetch and depth.
Implementation Method 1
the turbulent shear stress is related to disturbance of waves to airflow... and thus a Froude number is used to represent a strength of interaction between the turbulent terms in airflow and waves
Implementation Method 2
the viscous shear stress is related to the surface currents... and thus a Reynolds number is used to represent the strength of the interaction between the viscous terms in airflow and the surface currents
Data Source
AI summary
The present invention discloses a method and system for a wind stress coefficient expression by comprehensively considering impacts of an average wind speed, a fetch and a water depth, and relates to the field of wind-wave-current numerical simulation studies. Based on a wind-wave-current coupling interaction mechanism in lakes, oceans and other waters, two dimensionless numbers that can represent a wind-wave-current interaction strength: a fetch Froude number and a fetch Reynolds number, are constructed, a form of a wind stress coefficient expression with an undetermined coefficient is established, and then the undetermined coefficient is obtained by using a nonlinear regression method with reference to experimental and measured data to obtain a final wind stress coefficient expression. The present invention overcomes the shortcomings that a conventional wind stress coefficient expression considers only an impact of a single factor of wind speed, and breaks through the limitation that it is difficult to adapt to numerical simulation of lakes. A verification result of a Lake Tai water level shows that the constructed wind stress coefficient expression is more reasonable and superior. The present invention can be widely applied to the field of wind-wave-current numerical simulation studies on lakes, oceans and other waters.