How is lift created on sails?5 answersLift on sails is primarily generated through the manipulation of the vorticity field and the impulse theory. The force production mechanisms involve the continuous generation and shedding of vortex rings from the sail's perimeter, leading to the creation of leading and trailing edge vortices that contribute to the overall sail force. This force can be computed using the Kutta-Joukowski lift formula, the strength of vortices, or the vorticity flux at the sail's perimeter. The sail's aerodynamic efficiency is enhanced by adjusting the sail shape based on the vorticity field, allowing for improved performance and speed gains of up to 15-25%. By understanding these mechanisms, designers can optimize sail shapes for maximum lift and minimum drag, ensuring stable and efficient sail systems.
What is the vertical force variation during a seismic isolator experiment?5 answersThe vertical force variation during a seismic isolator experiment is a critical aspect in earthquake protection. Research has shown that by utilizing innovative mechanisms like High-Static-Low-Dynamic Stiffness Systems (HSLDSS) and Quasi-Zero Stiffness Systems (QZSS), the force induced in the vertical spring of an isolator can be controlled and limited, regardless of displacement. Additionally, studies on base-isolated structures have highlighted the significant impact of vertical components of earthquakes on structural responses, such as increased compressive axial forces in columns and augmented tensile forces leading to local uplift phenomena in isolators. Experimental verification of design formulae for lateral force distribution on isolated structures has further emphasized the need for accurate modeling to account for higher mode effects during earthquakes, ensuring the effectiveness of seismic isolation systems.
Canard stability and lift effects5 answersCanard stability and lift effects are investigated in several papers. The aerodynamics and flow physics of a close-coupled canard configuration with a sharp leading edge are studied, showing that the lift, drag, nose-down pitching moment, and lift to drag ratio increase nonlinearly as the ride height decreases. Wind tunnel experiments of a Blended Wing Body (BWB) equipped with a canard as a longitudinal control surface reveal that the lift coefficient does not change much with different canard setting angles, but the moment coefficient increases as the canard setting angle is increased. Another study on the effect of canard setting angle on the aerodynamic characteristics of a BWB shows similar results, with the lift coefficient increasing with increasing angles of attack at any canard setting angle. The impact of canard trailing vortex flow interactions on the aerodynamic design and flight performance of fin-stabilized munitions is also investigated, indicating that designs that do not consider canard trailing vortex interactions suffer from underpredicted stability. Finally, experiments on simple close-coupled canard configurations with different canard's swept angles and jet momentum coefficients show that the lift increment and critical stall angles increase with increasing canard's swept angles, and that controlling the wing vortex is possible by canard-spanwise blowing.
How does the front wing design impact the aerodynamic balance of the entire car?4 answersThe front wing design has a significant impact on the aerodynamic balance of the entire car. Installing a straight wing in front of or above the body can affect the aerodynamic characteristics, particularly the aerodynamic downforce values of the front wheels. Multi-element wings with wingtip devices can also influence the structural behavior of the wing and degrade its aerodynamic performance. The addition of a Gurney Flap to the front wing can dramatically improve its performance by increasing the downforce while minimizing the increase in drag force. The design of a lightweight front wing can effectively reduce the overall weight of the car, increasing its maximum speed and driving range. Overall, the front wing's design and components, such as additional wings or flaps, can enhance the aerodynamic performance and balance of the entire car.
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