THE DELIVERABLES
Large waves due to coastal storms (wind-waves) or tsunamis (in the form of solitary waves) will be simulated within the Multi-Hazards Simulator (MHS) using a wave generator. The wave generator consists of a flat “paddle”, which is a 1.5 m wide by 1.5 m tall rectangular plate that is hydraulically driven back and forth by a piston to generate a series of water waves. The wave generator action is controlled such that various wave trains can be created, regular or random, with controlled wave periods and amplitudes. Convenient software included with the system is used to specify the wave train. The control system also utilizes water wave sensors placed onboard the wave generator and within the MHS to adjust the piston action in real-time. This should enable the system to dampen reflected waves while continuing to generate the desired wave train.
The MHS Flume is built with a concrete wall on the south side and as a steel frame construction as the north wall, with glass panels. The flume has a total length of about 29.5 m from the east end to the west wall which delineates the outlet wall, a cross section of 1.5 X 1.5 m, with a maximum still water depth of 1.2 m. The flume is serviced by high-capacity pumps (2 x 0.5 m3/s = 1.0 m3/s) that draw from a large (300 m3) water storage reservoir situated below the flume bed. The section where the wave maker will be installed has a strong, reinforced concrete wall on both sides. Refer to Figure 1: Multi-Hazards Simulator. For further information regarding the installation site and current infrastructures, please refer to Appendix L – Investigation and Recommendation Study.
The new wave generator system must be manufactured and delivered as soon as possible. Therefore, the immediate planning for the wave generator system must be made in coordination with the users and the University of Ottawa Facilities team such that the construction works which is required for the installation to be also carried out to manage potential interfaces and dependencies immediately after contract awarding.
STATEMENT OF WORK
1. Background
1.1 - Requirements-Specifications and Environment
The wave generator system will be located at the east end of the MHS flume. The system shall be able to generate waves, with and against the main current /flow direction. At the same time, the wave generator must be equipped with an active absorption system to avoid and significantly reduce the occurrence of wave reflections in the test section of the flume. Ideally, the wave generator will be driven by a servo drive. It is expected that the actual stroke will be on the order of 1.8 m (+/- 0.8 m) and a usable stroke on the order of 1.6 m (+/- 0.8 m). The manufacturer should provide the performance curves for the wave generation capabilities within this specific flume. The wave generator and the actual wave board motion will be controlled via an included software (for Windows). The actual system of the wave generation (wet back or dry back) can be chosen by the Proponent as long as all given specifications are met. The flume is equipped with a raising gate located at its east end. Behind it, the flume discharges into a relatively opening (drain) into the underfloor reservoir. Alternative tenders for different systems will be accepted.
The wave generator system must be manufactured and delivered in conjecture with of the actual process of building the sediment recirculation system (built by the University of Ottawa) and seismic table (future RFP) components. The wave generator system will be installed and put in operation as a coherent system (including software and control system as well as an independent data acquisition system) by the supplier according to the specifications provided below as soon as the building process of the MHS Flume has advanced far enough to allow these steps.
Wave characteristics
The specification of wave parameters in order to define the necessary performance of the wave generator in terms of wave board stroke, velocity and acceleration is avoided herein by intention, as these actually depend on several factors, such as the underlying wave/wave theory or remaining reflections from the flume (nevertheless reflections will be avoided by the use of wave absorption system). Instead, the minimum requirements for the wave generator performance are defined directly to limit the wave generation capacity from the beginning. The manufacturer is expected to confirm the best technical solution at least for those requirements or even beyond and comment on the most critical aspects in terms of electrical power consumption and costs. Any suggestions for possible alternatives, which reduce purchase and operating costs, are expected.
1.2 - Technical requirements:
1.2.1 - The maximum water depth for wave generation will be 0.9 m and the minimum water depth for wave generation will be 0.3 m.
1.2.2 - It is anticipated that the wave generator will be running for about 1,000 hours per year with water depths between 0.5 m to 1.0 m in most cases.
1.2.3 - The maximum duration for continuous wave generation must not be less than 4 hours and need not be more than 10 hours.
1.2.4 - The wave generator must cope with the climatic conditions in the Hydraulic Lab in STEM, i.e.
- Humidity: The air conditioning system will be able to keep the humidity within the housing at around between 50 % and 80 % during regular operation. Nevertheless, the humidity might exceed these values and be at 100 % occasionally in the case of maintenance and model reconstruction. It should also be noted that condensation can occur on all components of the wave generator.
- Air temperatures between +10 °C and +40 °C.
- Water temperatures between +4 °C and +20 °C.
1.2.5 - The exposure of the parts of the wave generation system, that are submerged in the water during the operation of the flume, must be included in the category of corrosivity according to the current standards. The exposure of all other parts of the wave generator system, that are not submerged in the water but will constantly be surrounded by a high humidity and should also be included in a category of corrosivity. All parts need to be constructed according to these categories of corrosivity.
1.2.6 - The useful life for the wave generator system under the previously described climatic conditions without significant overhaul must be at least 25 years. The supplier must describe the required maintenance effort, cost and intervals.
1.2.7 - The wave generator must be piston-type with either wet back or dry back.
1.2.8 - The choice of a system with either a wet back or a dry back will be made by the bidder (alternative tenders for different systems will be accepted) and must take the following aspects into consideration:
- Increased danger of corrosion of all parts due to splashing water behind the wave paddles: All parts of the wave generating system need to be designed in a way to be able to withstand these circumstances and minimize the occurrence of splash water.
- Required space for the wave generating system: The whole wave generating system cannot use more than 3.5 m in length from the west edge of the drain opening of the flume. In case of a wet back system a passive absorber behind the wave paddles must be included in the calculations and in the tender.
1.2.9 - The height of the wave paddle must be 1.5 m, which corresponds to the height of the flume.
1.2.10 - The drive technology would ideally be electric (e.g., servo motors) rather than hydraulic.
1.2.11 - The usable stroke of the wave board (available for wave generation) should be in the order of 1.6 m (± 0.8 m), preferably more in order to maximize the capabilities for the generation of long waves. A possible limitation for the maximum achievable stroke might be the limited available space between the end of the flume and the current sediment recirculation system outlet. These interfaces and dependencies with other parts of the planning processes of the flume must be coordinated with the customer in consent by the supplier.
1.2.12 - The maximum absolute wave board velocity must be at least 2.0 m/s. This comparatively high value is supposed to be needed in particular for the generation of highly nonlinear regular waves, where high velocities occur in the forward motion of the wave board to produce a steep wave crest. The velocity surely depends strongly on the underlying wave theory defining the wave board motion, e.g. for highly nonlinear regular waves the current in-house software has a special trochoidal theory implemented, which requires up to 50 % higher wave board velocities than simple linear wave theory in order to generate the steep crests and was the basis to determine the given minimum requirement.
1.2.13 - The maximum absolute wave board acceleration must be at least 3.0 m/s². These high accelerations typically occur with the generation of very steep waves at the wave crest or trough when the direction of the wave board motion changes. Due to the link to steep waves high accelerations only occur for a short moment in the order of a second, but in particular if steep irregular waves are generated it might be that the given value will be even exceeded for some fractions of a second. This should also be considered and the wave generator shall allow for very short higher accelerations than 3.0 m/s².
1.2.14 - The wave generator must include an active absorption system for absorption of generated waves during wave generation. The absorption system must work over the whole range of water depths given above and must also be able to handle changing water levels during operation.
1.2.15 - The wave generator must include emergency exit switches, which upon pressed stop the wave boards immediately, allow them to remain in their current positions and disconnect the whole system from the power supply.
1.2.16 - The whole wave generator system must be computer-controlled with a graphical user interface providing an overview of relevant condition parameters (e.g. temperatures, pressures, power consumption, wave board positions, velocities, and accelerations) and their control where applicable. The corresponding software must provide an API or an equivalent interface to allow for implementation of own software without conflicting safety issues.
1.2.17 - A computer and software for wave generation must be provided as well. The following requirements need to be met:
- Generation of regular waves with different theories (e.g. Airy, Stokes, cnoidal) by first and second order wave theory.
- Generation of irregular waves based on wave spectra (e.g. JONSWAP, TMA, Pierson-Moskowitz) by first and second order wave theory.
- Generation of solitary waves.
- Input of externally generated wave spectra and time series for water surface elevation, which are then converted to board motion by the software.
- Functionality to switch active absorption control on and off and to modify the parameters of the absorption algorithm.
- Saving of all recorded wave generator parameters, e.g. wave board stroke (actual and target), velocity and acceleration and water surface elevation where measured for wave absorption. Data must be saved in ASCII or binary file format with corresponding documentation.
- Regular updates and long-term support for the wave generating software have to be ensured for at least 10 years. An option for extension must be provided.
- The intended superimposition of waves with current might lead to varying water levels during a test and to wave characteristics within the flume that differ from target values. To account for the influences of the current superimposition, the control system must provide the possibility to account for changes of water level during operation.
The technical requirement listed above or proposed alternative should be provided and are expected to be included in the contractual agreement with the selected Proponent and use a performance measurement.
1.3 - Additional requirements aspects
1.3.1 - All interfaces and dependencies with other parts of the planning processes of the flume must be coordinated directly by the supplier with the general planner and the customer in consent. These include but are not limited to:
- Electrical power: Where is the power connection needed and how much power does the wave generating system need (diagram for average and peak values)?
- Cooling system, if cooling the motors is necessary.
- Sealing surface between the wave paddle and the walls of the flume (important in case of a dry back system).
- Dynamic forces: The bidders should explain how will, during wave generation, occurring forces be transferred into the supporting construction of the MHS flume? How large will these forces be?
1.3.2 - The planning processes of the other components (seismic table and sediment recirculation system) progress parallel to the planning of the wave generator system. Therefore, not all parameters can be finally decided on in advance. If the further planning processes of the components induce a change of some of the given parameters of this document (for example the usable stroke or the available space and thus the system length of the wave generator) before the agreed-on freeze date, the wave generator system must be adapted accordingly.
1.3.3 - Installation of the wave generator: how will the wave generator be installed in the flume using the available 5 t crane. Note that the wave generator and its connection to the wall will need to be moved out of the flume using the crane above.
1.3.4 - Required infrastructure on site, interfaces, and media access that are necessary for installation and operation of the wave generator, e.g. access to internet, electrical power and fresh water, must be described.
The wave generator system is considered as a complete system, which has to fulfil all given technical requirements including, but not limited to, its proper installation in the flume. Therefore, all aspects mentioned above which are essential to warrant the functionality and operability of the whole wave generator system are within the responsibility of the supplier.
It should also be noted that the correctness and precision of the provided figures and plans cannot be guaranteed but shall be consider as orientation for preliminary planning. Therefore, it is mandatory for the supplier of the wave generator system to confirm all boundary conditions and acquire the precise geometrical dimensions on his own from the general planner after they would be awarded the contract.
-
