ui <- shinyUI(fluidPage(
  fluidRow(
    column(12,
      "Fluid12",
         fluidRow(
           column(3,
             "Fluid3",
             numericInput('H_lbv', 'Height - lower bound', 10),
             numericInput('H_ubv', 'Height - upper bound', 21),
             numericInput('D_lbv', 'Diam. - lower bound', 8),
             numericInput('D_ubv', 'Diam. - upper bound', 16),
             numericInput('ro_lbv', 'Dens. - lower bound', 0.3),
             numericInput('ro_ubv', 'Dens. - upper bound', 1.0)
             ),
           column(width = 9,
               "Fluid9",
               fluidRow(
                       column(3,
                              plotOutput("plot")),
                       column(width=3,
                              plotOutput("plot2")),
                       column(width=3,
                              plotOutput("plot3"))
               ), fluidRow( ## I thought this would work to add the second row
                       column(width=9,
                              plotOutput("plot3"))
               )
           )
         )
      )
  )
 )
)