Deformable Hydrofoil Designs

Inspired in part by . . .
Morphing Hydrofoil Model Driven by Compliant Composite Structure and Internal Pressure
Keywords: Smart-Structure, Hydrofoil, Morphing, Compliant, Composite, Cavitation

In this work, a collaborative experimental study has been conducted to assess the effect an imposed internal pressure has on the controlling the hydrodynamic performance of a compliant composite hydrofoil. It was expected that the internal pressure together with composite structures be suitable to control the hydrodynamic forces as well as cavitation inception and development.

A new concept of morphing hydrofoil was developed and tested in the cavitation tunnel at the French Naval Academy Research Institute. The experiments were based on the measurements of hydrodynamic forces and hydrofoil deformations under various conditions of internal pressure.

The effect on cavitation inception was studied too. In parallel to this experiment, a 2D numerical tool was developed in order to assist the design of the compliant hydrofoil shape. Numerically, the fluid-structure coupling is based on an iterative method under a small perturbation hypothesis.

The flow model is based on a panel method and a boundary layer formulation and was coupled with a finite-element method for the structure. It is shown that pressure driven compliant composite structure is suitable to some extent to control the hydrodynamic forces, allowing the operational domain of the compliant hydrofoil to be extended according to the angle of attack and the internal pressure. In addition, the effect on the cavitation inception is pointed out.

Read the full article here . . .

Muiren, As a retired Rotor-blade designer (EC135) morphing was looked at intensely … the issue is ensuring a benign Failure Mode of the morphing actuation system and getting “down/home” safely with minimal control degradation … a guaranteed stable “neutral” position is necessary for this to happen.

That would still be true with any conventional high performance submerged hydrofoil design, because as you obviously know they have to be continuously adjusted.

In my experience any fly-by-wire system be it car, motorcycle, aircraft requires that same safety consideration.

I don’t know any Systems Analyst or Engineer that doesn’t start with that assumption, so were you cut off in mid thought, was some a point you where leading up to that adds value to the discussion?

I have always worked within “Fail-Safe” constraints under FMECA … probability statistics were introduced with the MBAs … the result was aptly illustrated with the 737MAX. My comment was meant to create awareness that safety critical functionality are currently being eroded by economics. If the product cannot be made safe and sold as such, then it should be deprecated or abandoned as not fit for use. Ethics demand this. my 2cents

I appreciate the point, my point being the hope you had more than 2 cents to add.

Since the nature of my post is discussion of “Prior Art” and speculation on adapting it to a series of relatively low-cost test mules as my own interest, this premature concern for “safety” is not specific to the topic and with no evidence to assumes I lack the competence to address safety when the practical context demands it. I am not easily offended when people, for whatever reason, are motivated to presume me incompetent while insinuating they are just trying to be helpful.

Simple question.

Did you study the paper and do you have 2 cents or more to contribute to the topic subject: Deformable Hydrofoils?

Are you interested in demonstrating the presumption of mutual aid, the raison d’être of the forum, and share what you know already about the topic, or have found since reading my post, when you of course did your own research on the subject?

sorry, I appear to have given you the wrong impression about my comments … I have always endeavored to be non-personal with them. I have no issue with pneumatic actuation (inflation), my experience with composites has always been to design to required structural stiffness and overall strength will always fall into place so … when introducing compliancy in order to properly actuate a surface, one requires full time pneumatic pressure to maintain the shape. However with hydraulic and electrical actuation, secondary and even tertiary systems are required. So, what can one do with a pneumatic control system? At EC we went with piezoelectric actuators with a marginally compliant TE … it returned to a neutral position when failed, and we gained some dB … Benign Failure. As this was a series bound component, the full operating Spectra WITH Scatter Factor was tested with a Blade Life MTBF … To introduce a morphing Sweep or Twist into the blade (ie high mu) performance was/is considered very high risk to safety of flight. Secondary Controls on an eFoil for trimming actions may be demonstrated to be suitable, provided a return to neutral can be shown. I recently saw a paper for a foiling Moth where the entire wing had +/- 10deg AOA movement, it was mechanically actuated and inspectable at all times. Safety costs and is never required until it is required … failure will always come back to the designer, no amount of liability insurance will mitigate it … 5cents? :slight_smile:

A couple of things, there is no such thing as not-personal with human beings, that is an evidence-based opinion. That is high school level-gaslighting.

Second, this is the starting point of a discussion on I repeat prior art, meaning work already explored and in my professional opinion, found wanting. It is something most people need to know about any subject before envisioning anything new.

I personally think pneumatic actuation under the best conditions lacks the power, speed, or precise needed to accommodate the forces encountered in real-world applications. It is a low-cost means of exploring in a test environment which I am sure you already know.

Can you name a critical application like an aircraft were they are used? Think smaller then, name a motorcycle that has pneumatic brakes, a car with pneumatic steering?

As you must already know, advanced hydraulic or more accurately electro-hydraulic actuators have been the standard for a long time, with a new generation of extremely compact but powerful units with embedded sensors appearing a few years ago, but again, none of that has any bearing on having a free discussion.

Let me add that my personal research has been in the suitability of ferromagnetic fluids, synthetic muscles, active origami.

My I suggest an open mind and talk with instead of at me. Not a single paragraph resembles an attempt at cooperative collaboration. Nothing in your grammar suggests a mode of discourse. Stop trying to derail my topics and treating them like your classroom and us your students.

Murien, this link is to a paper on “Shape-morphing carbon fiber composite using electrochemical actuation” describes a concept that I consider appropriate for morphable structures. The bondshop will need to “step-up” a bit, but the end-item functionality increases the value significantly over static mechanically structures. The new “material” can be physically characterized for A/B Basis physical properties with the actuation functionality “grading” similar to CPU Chips in the wafer mfg process. The ability to “fail” to a safe predetermined geometry when V is removed, it should also reduce the requirements for backup systems.