Visualizing the crack driving force through fluid analogy

It is shown that the crack driving force for a fundamental antiplane crack problem is analogous to the limiting case of the force acting on an ideal fluid on free streamlines that form at the ends of flow around two parallel plates.

ALMA discovery of a rotating SO/SO2 flow in HH212

We wish to constrain the possible contribution of a magnetohydrodynamic disk wind (DW) to the HH212 molecular jet. We mapped the flow base with ALMA Cycle 4 at 0.̋13 ~ 60 au resolution and compared these observations with synthetic DW predictions. We identified, in SO/SO2, a rotating flow that is wider and slower than the axial SiO jet. The broad outflow cavity seen in C34S is not carved by a fast wide-angle wind but by this slower agent. Rotation signatures may be fitted by a DW of a moderate lever arm launched out to ~40 au with SiO tracing dust-free streamlines from 0.05−0.3 au. Such a DW could limit the core-to-star efficiency to ≤50%.

Flow Induced Rotation of a Flat Plate Subjected in Uniform Current Based on the Streamline Theory

This work describes the behavior of a vertical flat plate free to rotate in uniform current. The intention of this research is to study the fluttering problem that may occur with falling objects in water such as a manifold during the pendulous installation method (PIM). The free streamline theory is applied here to investigate the steady, two-dimensional flow at a given angle of attack past a flat plate with a fully developed wake. The leading and trailing edges of the plate are assumed to be sharp and the flow configurations are such that the free streamlines separate from the plate at these sharp edges, the thickness of the flat plate is assumed to be of zero. The Roshko’s model will be used to approximate the wake far downstream. The moment coefficient formulation has been calculated for different angles of attack yielding good accuracy with experimental results. This includes the existence of a natural frequency for small amplitude oscillations. The free-streamline theory confirms that the natural frequency is linearly proportional to the incoming flow velocity.

Jet-Plate Interaction for Wedge-Shaped Plates of Arbitrary Angles

An investigation has been undertaken to study the problems of jet-plate interaction through the method of hodograph transformation. The physical flow field is first transformed to a hodograph domain. By using properly selected flow parameters, the solution is established through numerical computations with rectangular grid in the hodograph plane. The resulting plate configuration, the free streamlines, and the flow properties in the physical plane are subsequently obtained through direct numerical integration. Jet flows toward wedge-shaped plates of arbitrary angles are solved to demonstrate the ability of the method. To verify the solutions, momentum principle has been employed in the physical plane for all test cases. It is found that the results obtained through this method are satisfactory.

A wake singularity potential flow model for airfoils experiencing trailing-edge stall

An incompressible inviscid flow theory for single and two-element airfoils experiencing trailing-edge stall is presented. For the single airfoil the model requires a simple sequence of conformal transformations to map a Joukowsky airfoil, partially truncated on the upper surface, onto a circle over which the flow problem is solved. Source and doublet singularities are used to create free streamlines simulating shear layers bounding the near wake. The model's simplicity permits extension of the method to airfoil-flap configurations in which trailing-edge stall is assumed on the flap. Williams’ analytical method to calculate the potential flow about two lifting bodies is incorporated in the Joukowsky-arc wake-singularity model to allow for flow separation. The theoretical pressure distributions from these models show good agreement with wind-tunnel measurements.