Dr Heide Friedrich's Personal Pages

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Available research projects for BE, ME, PhD are accessible here.

Heide Friedrich's research projects:

Project description:
The principal aim of this research project is to investigate the effect that clay has on turbidity current flow structure and deposit textural variation, from a series of controlled laboratory experiments. Clay types will match those observed within Waitemata Basin sediments sampled from turbidite beds.

Design of artificial surf reefs - experimental study
Investigators: Heide Friedrich
Students: Alistair Briffet, Alistair Hancox

Project description:
The artificial Narrowneck surf reef was a world's first on completion in 2001. Narrowneck reef is part of the Northern Gold Coast Beach Protection Strategy, with the primary objective to widen the beaches and mitigate storm erosion and a secondary objective to provide better surfing. The artificial reef is located three meters underwater, so needs a three-meter swell to break. Over the last years it has created its own little ecosystem, with lobsters, turtles and various fish all currently calling the reef home.

Since then construction started on a second artificial surf reef in Mt Maunganui, located on the northeast coast of New Zealand, inside the Bay of Plenty. Additionally to these two reefs, a smaller reef was completed in El Segundo, California, Pratte's Reef.

The following issues are involved when researching artificial surf reefs:
-  Beach Protection and Dynamics
-  Design of artificial reefs, case studies, natural reefs
-  Surfing Science (Basic research about surfing, sport kinematics)
-  Reef Ecology (Ecological benefits, monitoring, artificial and natural reefs)
-  Coastal management, planning and economics
-  Construction methods (Ways to build multi-functional reefs, longevity, stability)
-  Risk Management (Future of the coast, Greenhouse, long-term goals)

Project description:
This study aims to prepare a report on the current knowledge about artificial surf reefs, in respect to environmental, ecological, and design aspects. Based on the report a design for a surf reef needs to be proposed and tested in the wave flume at the Fluid Mechanics Laboratory. During the experimental phase attention should be given to scale issues and wave breaking patterns. Based on the results of the study, follow-up studies shall be suggested.

Gravel-bed river experiments
Investigators: Prof Bruce Melville, Heide Friedrich
PhD Student: Katherine Heays

Dependency of catchment size on runoff hydrograph
Investigators: Heide Friedrich
MEng Student: Yudan Liang

Hydraulics of complex stormwater outlet structures
Investigators: Dr Elizabeth Fassman, Heide Friedrich
Students: Jimmy Ho

Project description:
The hydrologic design basis for most stormwater treatment devices such as constructed wetlands and detention basins is to reduce peak flow for discrete rainfall events. The outlet structures which enable control usually incorporate multistage releases which may be comprised of a perforated riser or plate for very low flows (water quality release), small rectangular weirs for low-medium flows, and large circular or box weirs that transition from weir flow to orifice flow for high flows.

Model experiments: influence of floods on sediment deposits in rivers equipped with groynes
Investigators: Heide Friedrich
Students: Remy Gasset, 2007; Guillaume Weber, 2008

Project description:
Research of the behaviour of groyne structures during floods is topical. However, flood effects on sediment layers situated in groyne fields of large rivers are still not well understood. Sediment layers, often strongly polluted and restricted in their movement by groyne structures, represent a hazard for the river and its neighbouring floodplains during high discharge events. The erosion effects of floods on these sediment layers are focused on herein. A model of several groyne sections of a straight river stretch and its near floodplain ? representative of the Rhine and Elbe Rivers ? was built in a wide laboratory flume. The influence of flood discharges on sediment deposits in groyne fields was studied by evaluating the flow fields and the sediment transport in the main channel and floodplain of channels with groyne fields. The locations and geometries of the main flow structures and erosion patterns are identified. The experiments show that even during flood discharges the groyne fields act as dead water zones and minimal erosion occurs. Additionally, three different flow patterns are identified for the groyne. For emerged groynes a double-eddy pattern for normal winter discharges and a one-eddy pattern for a summer discharge are observed. Conversely, for submerged groynes, the flow at the water surface was mostly unidirectional. The results are discussed in relation to river pollution and biodiversity.

Friedrich, H., Gasset, R. and Melville, B.W. (2008). " Model Experiments: Influence of Floods on Sediment Deposits in Rivers equipped with Groynes", paper submitted to 4th International Conference on Fluvial Hydraulics (River Flow 2008), Izmir, Turkey, 3-5 September.

Statistical properties of dune profiles
Investigators: Heide Friedrich, Andries Paarlberg, Joost Lansink

Project description:
A set experiments for dunes developing from a flattened sand bed was obtained in a narrow 0.44-m-wide and 12-m-long glass-sided open channel. The sand in use was a coarse uniform sand of D50=0.85-mm and was exposed to a series of steady and uniform flow conditions. The chosen flow depths generated practically 2D dunes in flow direction over the length of the channel. Spatial sand-bed-elevation profiles were recorded on the centreline of the flume over a distance of 6-m, roughly every 23-sec over the time of development. The recorded dune geometries were evaluated with both the discrete and the continuous approach. For the discrete approach, discrete height and length values are obtained for dunes. For the continuous approach, the second-order distribution moments, standard deviations, were used to obtain characteristic height and length values of the dune field. It is shown that a lack of clear definitions for the discrete approach results in a wide range of averaged dune geometries, depending on how thresholds were set during the analysis process. The continuous approach provides more objective results, but interpreting the results of the analysis requires careful consideration. For this paper, the analytical results of applying both approaches are compared. A preliminary correlation between both approaches is discussed. The physical relationship between the flow field and characteristic height and length values, as obtained through the continuous approach, is not yet clear.

Friedrich, H., Paarlberg, A.J. and Lansink, J. (2007). Evaluation of statistical properties of dune profiles., Proceedings of the 5 th IAHR Symposium on River, Coastal and Estuarine Morphodynamics (RCEM 2007), Twente, The Netherlands, 1-10, 17-21 September.

Underwater Bedforms
Investigators: Heide Friedrich - ongoing from PhD project

Project description:
This study investigated the initiation and development of bed forms from a flattened sand bed to equilibrium conditions in laboratory flumes. Bed-form initiation was studied visually and observations support the position that initial disturbances on a flat sand bed are caused by turbulent sweep events. New insights are obtained on pattern analysis during early bed-form development, on the development of dunes in fine sand and on the 2D-3D dune transition in coarse sand. A flume comparison study is carried out and a synopsis on why bed forms occur in river environments is presented.

Experiments were undertaken in two flumes at The University of Auckland, a narrow 11.9-m-long, 0.38-m-deep and 0.44-m-wide glass-sided open-channel flume and a wide 45-m-long, 1.2-m-deep and 1.5-m-wide glass-sided open-channel flume. A fine uniform sand with D50 = 0.24-mm and a coarse uniform sand with D50 = 0.85-mm were utilized for the experiments. Flows ranging from 0.35-m/s to 0.81-m/s and water depths between 0.15-m and 0.52-m were used.

The development of bed forms was recorded with an array of 30 Multiple Transducer Arrays (MTAs) from Seatek. The acoustic sensors were arranged in a grid structure, covering the centre 40% of the flume width for the narrow flume and 90% of the flume width for the wide flume. A motorized carriage traversed the grid over a distance of 6.25-m for the narrow flume and 18.48-m for the wide flume, enabling 3D sand-bed elevation measurements every 1-min, and 2-min respectively, resulting in quasi-4D bed-form development records.

Moving probe measurements (46 experiments all together) were obtained until the bed forms were fully developed, ranging from 2.5-hrs up to 7.5-hrs for individual flow conditions. Once the bed forms had developed, the MTAs were positioned on a different grid, in order to record in stationary mode the passing by of bed forms under steady flow conditions. The stationary probe measurements ranged from 6-hrs up to 16-hrs for 48 experiments in total.

Continuous analysis tools are introduced, treating sand-bed elevations as a random field, compared to the conventional discrete analysis methods. These random field analysis tools are applied to study topographical changes during the dune development in fine sand and the 2D-3D dune transition for coarse sand.

A flume comparison study between the narrow and the wide flume was carried out. Individual experiments with similar flow conditions are compared in regards to bed-form development. Power law relations are analyzed and discussed.

Friedrich, H. and Melville, B. W. (2008). Pattern Observation During Bedform Development. Paper accepted for World Environmental & Water Resources Congress 2008 (EWRI-2008), Honolulu, Hawaii, USA, 12-16 May.

Coleman, S.E., Nikora, V.I., Melville, B.W., Goring, D.G., Clunie T.M. and Friedrich, H. (2008). SWAT.nz: New-Zealand-based Sand Waves and Turbulence Experimental Programme, Acta Geophysica, Online First, 1-23.

Clunie, T.M., Nikora, V.I., Coleman, S.E., Friedrich, H. and Melville, B.W. (2007).  Flow measurement using flying ADV probes, Journal of Hydraulic Engineering, 133(12), 1345-1355.

Friedrich, H., Melville, B.W., Nikora, V.I. and Coleman, S.E. (2007). Flume Influence on Developing Dune Beds, Proceedings of the XXXII IAHR Congress, Venice, Italy, 1-10, 2-6 July.

Coleman, S.E., Nikora, V.I., Melville, B.W., Goring, D.G., Friedrich, H. and Clunie T.M. (2007). New Zealand Programme of Sand Waves and Turbulence Research: SWAT.nz, Proceedings of the 6th International Symposium on Ecohydraulics, Christchurch, New Zealand, 18-23 February  (poster on CD).

Friedrich, H., Nikora, V.I., Melville, B.W. and Coleman, S.E. (2006). Statistical Interpretation of Geometric Differences in Ripple and Dune Shapes for Developing Beds., Proceedings of the 7th International Conference on Hydroscience and Engineering (ICHE-2006), ISBN: 0977447405, Philadelphia, USA, 1-14, 10-13 September.

Friedrich, H., Melville, B.W., Coleman, S.E., Clunie T.M., Nikora, V.I. and Goring, D.G. (2006). Three-dimensional properties of laboratory sand waves obtained from two-dimensional autocorrelation analyses, Proceedings of the 3rd International Conference on Fluvial Hydraulics (River Flow 2006), Lisbon, Portugal, 1013-1022, 6-8 September.

Friedrich, H., Melville, B.W., Coleman, S.E., Nikora, V.I.and Clunie T.M. (2005). Three-dimensional measurement of laboratory submerged bed forms using moving probes, Proceedings of the XXXI IAHR Congress, Seoul, Korea, 396-404, 11-16 September.

Clunie T.M., Coleman, S.E., Melville, B.W., Friedrich, H.,  Zhang and Nikora, V.I. (2004). Temporal development of sediment wave magnitudes, Proceedings of the 5th International Symposium on Ecohydraulics, Madrid, Spain, 851-856, 12-17 September.

Friedrich, H., Coleman, S.E., Melville, B.W.andClunie T.M. (2004). Development of discrete subaqueous bed forms, Proceedings of the 2nd International Conference on Fluvial Hydraulics (River Flow 2004), Naples, Italy, 761-768, 23-25 June.



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