Bernoulli pads can create a significant normal force on an object without contact, which allows them to be traditionally used for non-contact pick-and-place operations in industry. In addition to the normal force, the pad produces shear forces, which can be utilized in cleaning a workpiece without contact. The motivation for the present work has been to understand the flow physics of the Bernoulli pad such that they can be employed for non-contact biofouling mitigation of ship hulls. Numerical investigations have shown that the shear stress distribution generated by the action of the Bernoulli pad on the workpiece is concentrated and results in maximum shear stress very close to the neck of the pad. The maximum value of wall shear stress is an important metric for determining the cleaning efficacy of the Bernoulli pad. We use numerical simulations over a range of parameter space to develop a relationship between the inlet fluid power and the maximum shear stress obtained on the workpiece. To increase the shear force distribution, we explore the possibility of adding mechanical power to the system in addition to the fluid power. The flow field between the Bernoulli pad and the workpiece typically involves a recirculation region and transition between laminar and turbulent flow. The maximum shear stress occurs in the vicinity of the recirculation region and to gain confidence in the numerical solver's ability to estimate these stresses accurately, experiments were conducted with a hot-film sensor.The main contributions of this work are as follows: a direct relationship is obtained between the maximum shear stress on the workpiece and inlet fluid power using dimensional analysis. A relationship between the maximum shear stress and the inlet Reynolds number is also obtained, and implications of these scaling relationships are studied. A direct relationship between the inlet fluid power and the shear losses motivates us to explore other methods of providing power to the system with the objective of increasing shear forces and thereby improving cleaning efficacy. We numerically investigate a Bernoulli pad in which additional mechanical power is added by rotating the pad. This additional power increases both the normal and shear forces on the workpiece for the same inlet fluid power. In the context of the rotating Bernoulli pad, it is found that for a given normal attractive force, a stable equilibrium configuration can exist for two different mass flow rates, with the higher mass flow rate resulting in a higher stiffness of the flow field. This phenomenon has not been reported in the literature. The wall shear stress distribution, obtained using numerical simulations, is validated using experiments for the first time. A constant temperature anemometer is used with a hot-film sensor and water as the working fluid; the sensor is calibrated using a fully developed channel flow. An experimental setup is designed to calibrate and later measure the wall shear stress in a Bernoulli pad assembly. The maximum wall shear stress is observed very close to the neck of the pad due to flow constriction and separation; the hot-film experiments accurately capture the magnitude of the maximum shear stress and its location. This provides us with confidence in the numerical solver, which can be used to optimize the Bernoulli pad design to improve its cleaning efficacy.
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