Channel Wing:
Project General Description
Team:Syrus Jeanes, Marco Herrera, Steve Bukowsky, Karl Lindman, Stephan Mehling, Joshua Gauvin,Anthony Costantini, Chris Buonocore,Omar Hayan,Michael Hanlon,Ben Holohan, Rob Radomski, Ted Simeoni
1.)Channel Wing Concept Description:
The Channel Wing was an idea conceived by an inventor named Willard Custer in 1950 as a tornado blew through his barn. He noticed a sudden change in pressure as the wind tore through the barn and carried it away. This gave him the idea to try the same idea with a wing. By enclosing the flow in a channel-like shape and constantly drawing air through with a puller prop he could ensure a constant, highly positive pressure gradient. The focus of our project is to attempt to prove that an aircraft can achieve vertical take-off and landing (VTOL) using channel wings. The basic concept is sound, it is up to us to achieve the goal.
Fig.1: Channel Wing Concept Fig.2: Custer Channel Wing Aircraft
1.1) Motivation:
Our motivation is to prove something that has never been done but merely speculated upon. By proving that a channel wing can achieve VTOL we can show that fixed wing aircraft can perform some of the same missions as helicopters with far less complexity.
1.2) Objective:
To prove that channel wings can achieve VTOL and thereby prove its effectiveness in traditional helicopter roles.
Fig. 3: Current Team Model Fig. 4: VTOL Channel Wing Forces
2.)Aerospace Engineering Disciplines:
Aside from providing the team with a great learning experience, our Channel Wing Project provides each and every team member with the opportunity to apply and practice many skills accumulated throughout our undergraduate career.
The initial application of a Systems Engineering Engine to our project provides the team with the opportunity to apply concepts and design processes practiced in industry. The ability to undergo a concepts development stage and then move on to a requirements phase provides the team with the confidence to move forward with the design. Being able to formulate a systematic design and testing process will be just as important as the calculations involved in the Channel Wing itself. Team cohesiveness and efficiency has been greatly improved through the application of these Systems Engineering concepts and skills.
Aerospace courses in fluid mechanics, solids modeling, aerodynamics, aerospace structures, and stability and control will become very important to the successful completion of our project. Team Channel Wing brings together various students with different strengths and skills that are relevant to the design, manufacturing, and testing of our prototype. The various subsystems of this project; wings, power, stability, structure, testing, calculations, and research will require the collaboration of all these various skills and strengths. It is the team’s intent to work towards the successful completion of our project, while being able to employ the knowledge from these various courses.
3.)Overview of Design Strategy
- Our overall goal is to demonstrate VTOL while implementing a Channel Wing.
- We will demonstrate that a Channel Wing is a “viable alternative” to a helicopter, depending on specified mission. This does not necessarily mean that it will be better than a helicopter. However, it will demonstrate a Channel Wing’s (fixed wing) ability to VTOL (concept demonstration).
- Strategy:
- Channel Wing Concept Validation
- With the use of the “Lift Stand”, demonstrate that the channel wing is indeed producing lift
- Straight Wing as a “Control”
- 9 in. and 14 in. straight wings
- Theoretical results have been obtained
- Run in wind tunnel and compare to theoretical results
- This will demonstrate the Wind Tunnel’s effectiveness in producing reliable data
- Channel Wing Theory
- Obtain as much theory as possible
- Run in wind tunnel to obtain effective span and scaling parameters
- Produce governing equations for Channel Wing characteristics
- Alpha Prototype of Straight Channel
- Stability and Control
- Payload, Power, and control surfaces integration
- Beta Prototype
- VTOL Channel Wing demonstration
- Implement lessons learned from Alpha Prototype
- Final Products
- Alpha Prototype
- Beta Prototype
- If Possible: Flow Visualization
- Channel Wing Governing Equations
- Understanding of Stability and Control for a Channel Wing aircraft
- “Channel Wing VTOL” Team publishable document
4.) Project Specifications
4.1)Effective Span
One of the greatest obstacles we discovered when trying to perform a simple analysis on a channel wing aircraft is that we had difficulty determining the span of a channel wing. For a straight wing it is the effective area producing lift. For a channel wing it becomes more difficult to determine, due to lift characteristics of the curved wing. We have constructed a 9 in straight wing, a 14.15 in straight wing and a 9 in channel. We will put all three models into the wind tunnel and by comparing the data we will obtain a dimensionless scaling parameter. This will enable us to satisfactorily approximate a channel of a given diameter to a straight wing of a given span for the same chord.
Metric:
The curves for the 9 in and 14.15 in wings will be compared for consistency. Once we have determined that they can be trusted, we will measure the actual lift force of the channel itself. Since we will know every variable in the lift equation except the span, we can calculate its effective span.
Units:
Dimensionless Parameter and Span (m)
4.2)Location of Aerodynamic Center
Before we can do further, detailed analysis we must know the location of the aerodynamic center of the wing. We have yet to find any literature that enables us to calculate this on our own so we must use wind tunnel testing. We will incorporate a 16 point pressure transducer, provided by Dr. Subramanian, into a channel wing and obtain the pressure profile through a channel with the propeller and the tunnel running. By using a steady-level assumption of T=D and knowing both the thrust and the CD of the channel wing, we can calculate what speed to run the tunnel based on the thrust being provided. This will allow us to accurately represent a normal flight condition for the pressure profile.
Metric:
Once the pressure profile is known, we can calculate the Moment about the leading edge and subsequently at any point along the wing. Knowing that Ma/c is constant for any α, we can then find the location of the aerodynamic center.
For the static VTOL case (i.e., 0 forward airspeed), the center of pressure will be the aerodynamic center.
Units:
Distance (m)
4.3)Velocity Profile
Once we have the pressure profile we can calculate the velocity profile through the channel for normal flight conditions. Using this and Fraude’s Momentum Theory analysis, we can derive expressions for the lift and moment of a channel of given diameter.
Metric:
Knowing the pressures obtained are dynamic pressures, we solve for the velocity in the q∞ expression. We then plot these velocities against the location along the wing to obtain the velocity profile. We are attempting to have largest area under curve as possible.
Units:
Velocity (m/s) and Distance (m)
4.4)Stable Flight
Due to the nature of the Channel Wing, we may run into trouble with static instability. Since a propeller is constantly drawing air over the active lifting surface, we expect the aerodynamic center to be further aft than for a normal aircraft. Also, the vertical distance between the aerodynamic center and the center of gravity is expected to be larger than on normal fixed-wing aircraft. Once we determine the location of the aerodynamic center, we can perform a stability analysis on the aircraft by using a simplifying assumption. At first, we will not attempt to model the aerodynamic effects of an actual channel wing; rather we will use our scaling parameter and perform the analysis using a comparable straight wing while ensuring that the centers of pressure and gravity are in the correct places.
Metric:
Use steady-level, pitching and rolling static stability equations to calculate a stable flight envelope.
For longitudinal stability,Cm > 0 and Cmα < 0.
For rolling stability, we still need to converse with Dr. Lee about roll stability since the textbook is rather sparse on the subject. We are continuing independent research on the subject as well.
Performance of these calculations will yield control surface areas and positions along the fuselage as well as an acceptable range of flight velocities and control surface deflection angles.
Units:
Degrees (°); Velocity (m/s) and Area (m2)
4.5)VTOL (Vertical Take-off and Landing)
This is the main focus of our project. The ability of a Channel Wing to perform VTOL was speculated upon in the 1950’s during the original Channel Wing tests. Since then, several research houses such as the Air Force and Georgia Tech have also suggested that Channel Wings are capable of VTOL. As of now, no one has ever performed this feat and documented the act. The potential of creating a fixed wing aircraft that can perform VTOL is what drew us to this project from the start. We plan to VTOL the aircraft in as light a wind as possible, preferably indoors. The first few trials will be tethered with the remaining trials un-tethered. The maximum altitude at which we will fly vertically and/or hover is dictated by what controller and transmitter we ultimately obtain.
Metric:
Calculate Lift of channel and Thrust of Prop/Motor combo. Calculate angle between the two forces that makes the resultant of those forces equal to the weight of the aircraft. We are aiming for highest L0/T0 possible.
Units:
Degrees (°) and Force (N)
5.) Constraints and Difficulties:
One of the main constraints of our project is the construction of the channel itself. We determined that the simplest, most cost-effective way of building the aircraft was via balsa construction. Balsa gives us a plentiful, cheap building material and is easy to work with. We lose strength and longevity of the aircraft but those are not crucial to our stated goal.
In addition, literature describing the theoretical calculations for the flight characteristics of a channel wing is almost non-existent. It is for this reason that the design process involves some early experimentation with the channel wing in a wind tunnel in order to determine some important parameters, which will then help us to determine theoretical results.
6.) Already Completed Work:
The Team has been diligently working on completing the design strategy for the Channel Wing Project. During Junior Design, the Team was able to finalize the initial concept studies and preliminary design survey. An extensive literature review has been very beneficial, as we learned what other universities and federal entities have already accomplished on determining the flight characteristics of a channel wing. The Team has also completed an initial structural test of three different fuselage configurations in order to determine the lightest and strongest variation. The construction of a channel wing has also been accomplished, in order to understand what difficulties may arise when finally manufacturing the wings for the alpha prototype. Also, several CAD drawings have been produced in order to portray the channel wing as a functioning prototype. Additional calculations, experiments, and analysis are required in order to produce a final design model.
7.) Future Work:
Current and future work will involve the acquisition of wind tunnel data for a straight and channel wing. It is also imperative that the team investigate the stability of a VTOL channel wing aircraft in order to help us understand the flight dynamics of the alpha prototype. Theoretical equations for the flight characteristics of a channel wing are also underway; this will provide us with the control values while experimentally determining various parameters.
8.) Testing
This semester we have an intensive wind-tunnel testing regime designed to give us the information we need to conduct a further, detailed design process. We will test a channel side by side with a number of straight wings to determine the effective span of a channel wing. That is, what is the span of a straight wing that will approximate the performance of a channel of a given diameter for gliding flight. Next, we will incorporate a 16 point pressure transducer into one of our channel wings and find the pressure profile of a channel wing with an active propeller. This will enable us to calculate a myriad of critical design metrics for the aircraft and vastly accelerate the project.
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