Tom Clifton: Fluid Flow: AntidunesAntidunes are bedforms that form in fast, shallow flows. I have been fascinated by them since I was 5. They were even the topic of my dissertation, but that was mainly so I could continue playing in the sand.(Untitled)- January 31, 2002 Last night, I posted a cleaner version of the box core image I put up last week. Apparently Canvas does not do as good a job generating jpegs from tiff images as Adobe ImageReady.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/31.html#a70 (Untitled)- January 28, 2002 Internal sedimentary structures produced by antidunes. The image is a positive print of an xray-radiograph taken of a box core from a stream that was manipulated to produce antidunes under aggrading conditions. The scale bar in the line drawing is 13 cm long. aggrading means sand was accumulating on the the stream bed, so that the stream bed was building up with time. Some amount of aggradation is necessary to preserve sedimentary structures until the sediments become rock.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/28.html#a58 (Untitled)- January 26, 2002 I received a reprint of the antidune paper in Sedimentology that I mentioned last week. The paper describes sedimentary structures produced by antidunes in a laboratory flume. The study shows many of the features that I described in my dissertation. The one thing that is missing from the study is an explanation of how the internal sedimentary structures that they observe are produced by antidunes. There is not a clear explanation of what is happening on the bed to produce the structures. I...http://radio.weblogs.com/0100021/categories/antidunes/2002/01/26.html#a51 (Untitled)- January 19, 2002 Macro error: Can't evaluate the expression because the name "116875776" hasn't been defined. Antidunes in the wild. This picture shows the surface waves breaking above antidunes in San Gregorio Creek, CA. Antidunes often display a behavior of building until the surface wave above them breaks and disrupts the flow over the bedform. The stream is flowing left to right.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/18.html#a26 (Untitled)- January 19, 2002 Macro error: Can't evaluate the expression because the name "116875776" hasn't been defined. This schematic shows basic form of an antidune. The stream bed is deformed into a set of waveforms (bedforms) with a definite crest and trough. The water surface is also deformed into a similar waveform. The water surface waveform is in-phase with the bedform. The water current is flowing from left to right while the bedform migrates from right to left.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/18.html#a25 (Untitled)- January 18, 2002 Antidune Basics Antidunes are in-phase bedforms that form on a sandy substrate beneath super-critical flows. Antidunes migrate upstream against the current flow, opposite the migration direction of most bedforms (such as dunes and ripples). What does this mean Antidunes are type of bedform (any regular, wave-like form that occurs on a channel bed). Antidunes are in-phase with the water surface above them, so the crest and trough of the antidune are matched by a crest and trough in the water's.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/18.html#a24 (Untitled)- January 18, 2002 Last night I found the archives of my antidune data, texts, and graphics. Today's challenge will be finding the old applications to access the files. Does anyone have an old copy of Personal Press that I could borrowhttp://radio.weblogs.com/0100021/categories/antidunes/2002/01/18.html#a20 (Untitled)- January 17, 2002 Hey, it looks like people are still working on antidunes. Here is an abstract from an article that is in press in Sedimentology.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/17.html#a19 (Untitled)- January 17, 2002 Here is a quicktime movie of antidunes in a flume.http://radio.weblogs.com/0100021/categories/antidunes/2002/01/17.html#a17 |