On the interaction between turbulence grids and boundary layers

Turbulence grids are widely used in wind tunnels to produce representative turbulence levels when testing aerodynamic phenomena around models. Although the purpose of the grid is to introduce a desired turbulence level in the freestream flow, the wall boundary layers of the tunnel are subjected to modification due to the presence of such grids. This could have major implications to the flow around the models to be tested and hence there is a need to further understand this interaction. The study described in this paper examines wind tunnel wall boundary layer modification by turbulence grids of different mesh sizes and porosities to understand the effect of these parameters on such interaction. Experimental results are presented in the form of pressure loss coefficients, boundary layer velocity profiles and the statistics of turbulence modification

Developing a low-cost beer dispensing robotic system for the service industry

As the prices of commercially available electronic and mechanical components decrease, manufacturers such as Devantech and Revolution Education have made encoded motor controller systems and microcontrollers very accessible to engineers and designers. This has made it possible to design sophisticated robotic and mechatronic systems very rapidly and at relatively low cost. A recent project in the Autonomous Systems Lab at Middlesex University, UK was to design and build a small, automated, robotic bartender based around the 5 litre Heineken 'Draughtkeg' system, which is capable of patrolling a bar and dispensing beer when signalled to by a customer. Because the system was designed as a commercial product, design constraints focused on keeping the build cost down, and so electronic components were sourced from outside companies and interfaced with a bespoke chassis and custom mechanical parts designed and manufactured on site at the University. All the programming was conducted using the proprietary BASIC language, which is freely available from the PicAXE supplier at no cost. This paper will discuss the restrictions involved in building a robot chassis around 'off-theshelf' components, and the issues arising from making the human-machine interaction intuitive whilst only using low-cost ultrasonic sensors. Programming issues will also be discussed, such as the control of accuracy when interfacing a PicAXE microcontroller with a Devantech MD25 Motor Controller board. Public live testing of the system was conducted at the Kinetica Art Fair 2010 event in London and has since been picked up by websites such as Engadget.com and many others. Feedback on the system will be described, as well as the refinements made as a result of these test

Some observations of the behaviour of an adverse pressure gradient laminar boundary layer under wake impingement

The problem of laminar to turbulent transition in a boundary layer flow subjected to an adverse pressure gradient is relevant to many engineering applications. Under such conditions, the initially laminar flow within the boundary layer can undergo separation and then become turbulent upon reattachment, as transition is triggered by instabilities within the separated shear layer. In turbomachinery blades with high loading, the transition mechanism is further complicated by the presence of periodic wake disturbances shed by blades that move relatively in the upstream flow. The paper reports an experimental study of the effect of wake disturbances generated upstream on the development of a laminar boundary layer over a flat plate imposed with an adverse pressure gradient that is typical of a highly loaded front-stage compressor blade. Detailed velocity measurements using a hotwire are performed along the plate and the results are analysed both in the time domain and the frequency domain. Description of the major features identified is provided and the leading mechanisms that trigger the transition process are identified to be a possible combination of amplified Tollmien–Schlichting waves and the roll-up of vortices due to the Kelvin–Helmholtz instability of the separated shear layer

Investigating the use of unmanned plant machinery on construction sites

The UK Construction Sector has been estimated to contribute 8% of the UK’s GDP [1]. The worldwide recession has forced construction companies to introduce and adopt cost saving measures to increase productivity. Several robotic building systems are in development for the Construction Sector such as the PERI’s Automatic Climbing System [2] and Brokk’s remote-controlled demolition machines [3], but there has been little implementation on live sites. Construction sites by their very nature are dynamically changing environments, so if human input was removed entirely, a robot would need a high level of awareness of the current state of the building project in order to navigate and carry out its task

Development of a reconfigurable protective system for multi-rotor UAS

The purpose of this study is to illustrate how the design and deployment of a minimal protective system for multi-rotorcraft can cater for changes in legislation and provide for greater use both in and outdoors. A methodology is presented to evaluate the design and development of a system which protects both single axial and co-axial rotorcraft. The key emphasis of the development presented is the scenario in which the multi-rotorcraft can fly with increased speed including the capability of flying through windows and doors without the fear of system failure due to rotor disruption. Discussed as well is the degree of autonomy the reconfigurable system should feature as well as the effects of drag and added component mass to the performance of the system

Development of a low-cost SLAM radar for applications in robotics.

The current state of SLAM radar is quite advanced, featuring various methods of data retrieval. One of the methods used is that of video telemetry to locate “common spots” in the surrounding environment which provide positional information during motion. Another method is that of using high-speed high-resolution laser measurement tools which provide a 360° horizontal field of view and a 90° vertical field of view. These systems create vast amounts of point cloud data and are expensive, ranging from £1,000 upwards. These systems are often unsuitable for small competition robots due to these reasons. The developments discussed in this paper describes various alternative measurement technologies, such as ultrasonic and infra-red and how these can be adapted with the addition of a mechanical drive to provide an almost real-time 360° horizontal field of view and an adjustable vertical field of view

On the propagation of two types of disturbances through a laminar boundary layer subjected to separation and transition

The propagation of two types of artificial disturbances within a boundary layer is discussed. The boundary layer is initially laminar but later transitions to become turbulent through the formation of a separation bubble under the influence of an imposed adverse pressure gradient. The growth of the boundary layer and that of the disturbances within it are tracked experimentally using hotwire anemometry measurements. The effects of the interaction of the disturbances with the separation bubble are captured using both hotwire and particle image velocimetry measurements. For a chord based Reynolds number of 210 k it is shown that Kelvin–Helmholtz shedding frequencies over the bubble are unchanged in the presence of either of the disturbances and are comparable to the steady flow case with no disturbances present. Both disturbances produced an extensive calmed region on interacting with the bubble. The calmed region due to the bar wake is relatively longer and persistent. The upstream location of the separation bubble formation is unaffected by the disturbances, however the average size of the bubble is shown to be sensitive to the type of disturbance with the bar wake producing a thinner and shorter bubble

Heineken bot [a robot installation presented at the Kinetic Art Fair 2010]

Students from Middlesex University’s Product Design and Engineering Department have designed the ultimate drinks dispenser – the ‘Heineken Bot’, an automated robot, which can pour pints right in front of you! The Robot, a beer keg mounted on driveable wheels, has a specially programmed electronic brain which directs it to move along a specific route. By placing your hand above the Bot, a sensor is activated, which stops the device – you then place a glass under the keg tap, the Bot pours out your drink and moves on to its next customer! It could be the perfect solution for those tense moments ahead during this summer’s World Cup – no danger of missing that crucial penalty shoot-out