Try this:
$("select").val("3f2cb990-cd0e-4bfa-a23e-54701498a2e5");
or
$('select option[value="3f2cb990-cd0e-4bfa-a23e-54701498a2e5"]').attr('selected','selected');
To get By text: that contains ubuntu
$('select').find('option:contains("ubuntu")').prop('selected', true);
To get that contents ubuntu as well as 12.04
$('select').find('option:contains("ubuntu"):contains("12.04")').prop('selected', true);