Cálculo da força propulsiva gerada pela mão e antebraço do nadador através da dinâmica computacional de fluidos.

 

A.J. Silva¹

A.F. Rouboa²

L. Leal²

J. Rocha²

F.B. Alves³

A.M. Moreira⁴

V.M. Reis¹

J.P. Vilas Boas⁵

 

¹ Universidade de Trás-os-Montes e Alto Douro, Departamento de Ciências do Desporto, Vila Real;

² Universidade de Trás-os-Montes e Alto Douro, Departamento de Engenharias;

³ Universidade Técnica de Lisboa, Faculdade de Motricidade Humana;

⁴ Instituto Politécnico de Santarém, Escola Superior de Desporto;

⁵ Universidade do Porto, Faculdade de Desporto, Portugal.

 

 

RESUMO

A investigação da força propulsiva produzida pela mão e antebraço dos nadadores tem-se baseado em testes experimentais. No entanto, existem algumas dúvidas sobre a precisão e fiabilidade destes cálculos. Este estudo teve dois objectivos: i) dar continuidade ao uso da Dinâmica Computacional de Fluidos (DCF) como uma nova metodologia de investigação na Natação; ii) aplicar a DCF no cálculo dos coeficientes de resistência (C_r) e sustentação (C_s) resultantes da simulação numérica do fluxo externo da mão e antebraço. Para este efeito, utilizaram-se três modelos bidimensionais de um escoamento em regime permanente. Um modelo frontal (q=90º, F=0º) e dois modelos laterais, um tendo o dedo polegar como bordo de ataque (q=180º, F=0º), e o outro tendo o dedo mindinho como bordo de ataque (q=0º, F=0º). O sistema de resolução de equações utilizado foi o das equações de Navier-Stokes, para fluidos não compressíveis. Os principais resultados, demonstraram que o C_rfoi o coeficiente que contribuiu mais para a propulsão, sendo constante para toda a amplitude de velocidades com um valor máximo de 1,16. Com base nestes resultados, podemos concluir que: i) a DCF pode ser considerada uma nova metodologia susceptível de desenvolvimento para o cálculo de forças hidrodinâmicas em Natação (de facto neste estudo não se procedeu à respectiva validação, pelo que não se pode concluir pela sua validade); ii) nos três modelos estudados o C_s parece ter uma importância secundária na geração de força propulsiva.

Palavras-chave: CFD, modelos de turbulência, hidrodinâmica, sustentação, resistência.

 

ABSTRACT

Measurement of swimmer's hand/forearm propulsive forces generation using Computational Fluid Dynamics.

 

Propulsive force generated by swimmers hand/forearm has been studied through experimental tests. However, there are serious doubts as to whether forces quantified with these procedures are accurate enough to be meaningful. The main purpose of the present work was twofold: i) continuing the use of computational fluid dynamics (CFD) as a new tool in swimming research; ii) apply the CFD method in the calculation of drag and lift coefficients resulting from the numerical resolution equations of the flow around the swimmers hand/forearm. For these purposes three, two-dimensional, models of a right male hand/forearm were studied. A frontal model (q =90º, F=0º) and two lateral models, one with the thumb as leading edge (q=180º, F=0º), and the other with the litle finger as the leading edge (q=0º,F=0º). The governing system of equations considered was the incompressible Reynolds averaged Navier-Stokes equations. The main results reported that the drag coefficient was the coefficient that accounts more for propulsion, and was almost constant for the whole range of velocities, with a maximum value of 1,16 (C_d=1,16). Through the results, we can conclude that: i) CFD can be considered an interesting new approach for hydrodynamic forces calculation in swimming research; ii) in the three models studied the lift coefficient may be of secondary importance in force generation.

Key Words: CFD, turbulence models, drag, lift, hydrodynamics.

 

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CORRESPONDÊNCIA

António José Silva

Universidade de Trás-os-Montes e Alto Douro

Departamento de Ciências do Desporto

CIFOP

R. Dr. Manuel Cardona

5000 Vila Real

ajsilva@utad.pt